FFmpeg by Example

818 points 221 comments a day ago

hbn

I've enjoyed using ffmpeg 1000% more since I was able to stop doing manually the tedious task of Googling for Stack Overflow answers and cobbling them into a command and got Chat GPT to write me commands instead.

simonw

I use ffmpeg multiple times a week thanks to LLMs. It's my top use-case for my "llm cmd" tool:

  uv tool install llm
  llm install llm-cmd

  llm cmd use ffmpeg to extract audio from myfile.mov and save that as mp3

https://github.com/simonw/llm-cmd

resonious

I tried this (though with a different tool called aichat) for extremely simple stuff like just "convert this mov to mp4" and it generated overly complex commands that failed due to missing libraries. When I removed the "crap" from the commands, they worked.

So much like code assistance, they still need a fair amount of baby sitting. A good boost for experienced operators but might suck for beginners.

cm2187

Plus you need to know the format of your source file to design the command correctly. How many audio tracks, is the first video track a thumbnail or the video, are the subtitles tracks forced, etc.

And in some situations ffmpeg has some warts you have to go around. Like they introduced recently a moronic change of behaviour where the first sub tracks becomes forced/default irrespective of the original forced/default flag of the source. You need to add "-default_mode infer_no_subs" to counter that.

Philpax

I usually just paste the output of `ffprobe` into Claude when it's ambiguous. Works a treat.

Over2Chars

My feelings exactly, but I think that's OK!

It's another tool and one that might actually improve with time. I don't see GNU's man pages getting any better spontaneously.

Whoa, what if they started to use AI to auto-generate man pages...

BlaDeKke

> Whoa, what if they started to use AI to auto-generate man pages...

That’s the time to start my career in woodworking.

johnisgood

I already generate man pages (and POD) with Claude for my new projects. :D

It works really well.

assimpleaspossi

My experience exactly.

I no longer check with these AI tools after a number of attempts. Unrelated, a friend thought there was a NFL football game last Saturday at noon. Checking with Google's Gemini, it said "no", but there was one between two teams whose season had ended two weeks before at 1:00 Eastern Time and 2:00 Central. (The times are backwards.)

bityard

Do LLMs have knowledge of current events?

johnisgood

I mean, some are capable of searching the web.

Ask them about the fire in LA in 2025 January.

BiteCode_dev

Reading this feels like seing a guy getting his first car in 1920 and complaining he still has to drive it himself.

imiric

To me it's more like a guy getting his first car and complaining that the car is driving him in a direction that may or may not be correct, despite his best efforts to steer it where he wants to go. And the only way to know whether he ends up in the right place is to get out of the car, look around, and maybe ask more experienced drivers. Failing that, his only option is to get back in and hope to be luckier in the next trip.

Or he can just ditch the car and walk. Sure, it's slower and requires more effort, but he knows exactly how to do that and where it will take him.

LeoWattenberg

The beer brewers in my home town used to have a self-driving horse and cart which knew the daily delivery route going by all pubs and didn't really need a human to steer it or indeed be conscious during the trip. Expectedly, the delivery guy would get drunk first thing in the morning and just get carted about collecting the money.

pbhjpbhj

Pony & trap could be largely self-driving, after an initial training period. That would have been a distinct negative to "upgrading" for some, I'd imagine.

nine_k

It's speed and load capacity vs self-driving.

If we could imagine wiring a pony to control a car, its brain, while good at navigation, would likely be inadequate at the speed that a car attains.

shriek

Or maybe calling a cab and telling the cab driver each direction to get to the destination instead of the cab driver just taking you there.

atoav

Sell that guy probably got carried home by his horse after drinking half a bottle of whiskey, so maybe he had a point.

sdesol

> "convert this mov to mp4"

Did any of the commands look like the ones in the left window:

https://beta.gitsense.com/?chats=12850fe4-ffb1-4618-9215-c13...

The left window contains a summary of all the LLMs asked, including all commands. The right window contains the individual LLM responses.

I asked about gotchas with missing libraries as well, and Sonnet 3.5 said there were. Were these the same libraries that were missing for you?

resonious

Looking at this, I am pretty sure I also received a "libx264" clause. Removing it made the command work for me.

sdesol

I don't disagree that we need to be cautious with LLMs, but I've personally stopped asking GPT-4/GPT-4 mini for technical answers. Sonnet 3.5 and DeepSeek V3 (which is much cheaper but still not as good as Sonnet) are your best bet for technical questions.

Where I find GPT to perform better than Sonnet is with text processing. GPT seems to better understand what I want when it comes to processing documents.

I'm convinced that no LLM provider has created or will create a moat, and that we will always need to shop around for an answer.

wegfawefgawefg

everyone stopped using 4/4mini because theyre old.

4o replaced 4 back in April 2024. 01/01mini replaced 4o in Fall 2024.

stop using 4. use 01mini always. its cheaper, faster, and better.

o1/o1mini will be replaced by o3/o3mini in a couple months.

sdesol

Unfortunately you need to be tier 2 to use o1-mini. The only time I really use GPT is to summarize documents and for that, GPT-4o mini works well enough and it is significantly cheaper than other high quality models, so I never really rack up an OpenAI bill.

mistercheph

o1 is such a joke, worse than 4o in some ways like multiturn,

The months old sonnet feels a generation ahead of any OAI product I've used, I'll believe the hype on o3 when I see it, remember the sora and voice roll out?

wegfawefgawefg

You may want to reconsider this position.

I had this bizarre bug in rust networking code where packets were getting dropped.

i dumped all 20k lines into o1pro. it thought for about ten minutes and came back telling me that my packets had a chance of being merged if set in quick succession and i needed to send the length before each message and scan packets in a loop for subdivisions on the client. this bug hadnt happened before, only when running locally on a newer faster machine, and was frequent but hard to replicate.

it was correct, and provided detailed pseudo code to solve it.

the second case involved some front end code where during an auth flow ios would force refresh on returning to the browser causing authentication state to be lost. o1pro thought for about 5 minutes before telling me ios has a heuristic with which it decides to close an app on context switch based on available ram, etc, and that i needed to conditionally check for ios and store partial state in local store on leave assuming the app could be deloaded without my control.

it was correct. with some more back and forth we fixed the bug.

these are not the kinds of problems that claude and gpt<4 have been able to help with at all.

I also used voice, and video voice extensively for translation tasks in korea, japan, and taiwan, and for controlling japanese interfaces and forms for tax documents and software.

These are very good tools.

Philpax

o1 is not a general-purpose model, and it's not very good at multi-turn; it should instead be given all the context upfront: https://www.latent.space/p/o1-skill-issue

jack_pp

libx264 is the best encoder for h264 ffmpeg has to offer so it's pretty important you bundle it in your ffmpeg install. Those commands are perfectly standard, I've been using something like that for 10+ years

keeganpoppen

what exactly do you want the llm to do here? if the ask was so unambiguous and simple that it could be reliably generated, then the interface wouldn't be so complicated to use in the first place! LLMs are not in any way best suited for one-shot prompt => perfect output, and expectations to that effect are extremely unreasonable. the reason why LLMs are still hard for beginners to use is because the software is hard to use correctly. as with LLM output goes life itself: the results you get from using a tool can only ever be as good as the (mental) model used to choose that tool & the inputs to begin with. if all the information required to generate the output were contained by the initial prompt, then there would be absolutely no need to use the LLM at all in the first place.

Philpax

Hate to be that guy, but which LLM was doing the generation? GPT-4 Turbo / Claude 3.x have not really let me down in generating ffmpeg commands - especially for basic requests - with most of their failures resulting from domain-specific vagaries that an expert would need to weigh in on m

resonious

GPT-4

Philpax

Fair enough. If you remember what you were testing with, I'd love to try it again to see if things are better now.

Over2Chars

You have a fair point. Some LLMs are better at some tasks, and prompts can make a difference no doubt.

Perhaps at some point there will be a triage LLM to slurp up the problem and then decide which secondary LLM is most optimal for that query, and some tertiary LLMs that execute and evaluate it in a virtual machine, etc.

Maybe someday

NavinF

Oh I talked to some guys who started a company that does that. This was at an AI meetup in SF last year. They were mainly focused on making $/token cheaper by directing easy/dumb queries to smaller dumber models, but it also increases output quality because some models are just better at certain things. I'm sure all the big companies already have implementations of this by now even if they don't use it everywhere

Over2Chars

I was suggesting optimizing for answer quality, but optimizing for cost might be useful too I suppose for "business innovation" purposes.

th0ma5

Hate to be that guy, but which model works without fail for any task that ffmpeg can do?

iameli

"Writing working commands first try for every single ffmpeg feature that exists" is the highest bar I've ever heard of, I love it. I'm gonna start listing it as a requirement on job postings. Like an ffmpeg speedrun.

th0ma5

Yes and every failure of a product turns into a support ticket.

MzxgckZtNqX5i

Obligatory xkcd: https://xkcd.com/1168/.

hk__2

To be fair `tar` is quite easy to use once you understand the grammar of the options.

Philpax

I don't think there's a single human on or outside of this planet that can meet that requirement, but Claude has been pretty good to me. It's certainly a much better starting point than pouring over docs and SO posts.

th0ma5

In my experience you still get a lot of stuff that used to work or stuff that it just makes up.

AuryGlenz

I know I struggled on getting a good command to “simply” make the videos from my Z8 smaller (in file size).

Usually the color was wrong and I don’t care enough to learn about colorspaces to figure out how to fix it and it’s utterly insane how difficult it is even with LLMs.

Just reencode it as is but a little more lossy. Is that so hard?

latexr

Handbrake may be a better option for you. I find that for some tasks it’s not only simpler but straight up works better than FFmpeg.

https://handbrake.fr/docs/en/latest/cli/cli-options.html

bloqs

This doesnt exist in reality so in one sense, you could challenge the relevance

th0ma5

I think in the non LLM world though you at least have the trail of documentation you can unwind once you're in a bind. I don't care for prompt-a-mole fighting.

pmarreck

A while back I simply wrote my own bash function for this called `please`

as in

    bash> please "use ffmpeg to extract audio from myfile.mov and save it as mp3"

It will then courteously show you the command it wants to run before you agree to do it.

Here is the whole thing, with its two dependent functions, so that people stop writing their own versions of this lol. All it needs is an OPENAI_API_KEY, feel free to modify for other LLMs

EDIT: Moved to a gist: https://gist.github.com/pmarreck/9ce17f7996347dd532f3e20a2a3...

Suggestions welcome- for example I want to add a feature that either just copies it (for further modification) or prepopulates the command line with it somehow (possibly for further modification, or even for skipping the approval step)

mrweasel

While I love that that works, I still feel like just maybe ffmpeg needs a better interface. Not necessarily a GUI, just a better designed command line.

mvonballmo

Hypertalk <https://en.wikipedia.org/wiki/HyperTalk> lives.

dekhn

"The future is already here. It's just not very well distributed"

(honestly, the work you share is very inspiring)

zahlman

>This will then be displayed in your terminal ready for you to edit it, or hit <enter> to execute the prompt. If the command doesnt't look right, hit Ctrl+C to cancel.

I appreciate the UI choice here. I have yet to do anything with AI (consciously and deliberately, anyway) but this sort of thing is exactly what I imagine as a proper use case.

hnuser123456

Just like all other code. There will be user-respecting open source code and tools, and there's user-disrespecting profitable closed code that makes too many decisions for you.

atoav

Did you just invent the LLM-equivalent of curl-piping unread shell scripts into sh?

I am sure that will never cause any problems.

bspammer

It displays the generated command to you, there's an additional step to confirm.

atoav

Ah good to clarify, thanks

ykonstant

> Did you just invent the LLM-equivalent of curl-piping unread shell scripts into sh?

Many such cases.

Beijinger

uv?

phrotoma

like pip but written in rust

th0ma5

You should figure out what went wrong for the other commenter and fix your tool.

Waterluvian

I think I’m finally sold on actually attempting to add some LLM to my toolbelt.

As a helper and not a replacement, this sounds grand. Like the most epic autocomplete. Because I hate how much time I waste trying to figure out the command line incantation when I already know precisely what I want to do. It’s the weakest part of the command line experience.

Over2Chars

But possibly the most rewarding. The struggle is its own reward that pays off later many times over.

hbn

There are times I feel minor guilt for using an LLM to relieve brainwork, like figuring out an algorithm. That's probably a skill I should continue practicing for my own sake.

ffmpeg commands though? It's really not a practical skill outside of using ffmpeg. There's nothing really rewarding to me about memorizing awkwardly designed CLI incantations. It's all arbitrary.

Waterluvian

Not for me. It’s a tool I don’t care to use any more than I have to. I’m much more interested in what I’m using the tool to accomplish.

Over2Chars

I am not talking about the tool per se. I am talking about the skill of persistence and creativity in the face of a problem.

Learning a tool is useful, even invaluable, but if you don't have the persistence to use it, it's useless.

And many tools are just partially useful under some conditions. So creativity in using them is also useful.

So it's not about the tools, its about not giving up and trying different things, which makes all tools more effective, and problem-solving more likely.

Philpax

Yeah, and I'll do that with all of the tools and problems I actually care about :p

levocardia

For the longest time I had ffmpeg in the same bucket as regex: "God I really need to learn this but I'm going to hate it so much." Then ChatGPT came along and solved both problems!

zxvkhkxvdvbdxz

Interesting. Being able to use regexps for text processing through my career has probably saved me a few thousand hours of programming one-off solutions so far. It is one of those skills that really pays off to learn proper.

And speaking of ffmpeg, or tooling in general, I tend to make notes. After a while you end up with a pretty decent curated reference.

codetrotter

I use regexes a lot. The main thing that always trips me up is dealing with escaping, because different tools I use – vim, sed, rg, and so on – sometimes have different meanings for when to escape or not.

In one tool you’ll use + to match one or more times, and \+ to mean literal plus sign.

In another tool you’ll use \+ to match one or more time, and + to mean literal plus sign.

In one tool you’ll use ( and ) to create a match group, and $ and $ to mean literal open and close parentheses.

In another tool you’ll use $ and $ to create a match group, and ( and ) to mean literal open and close parentheses.

This is basically the only problem I have when writing regexes, for the kinds of regexes I write.

Also, one thing that’s not a problem per se but something that leads me to write my regexes with more characters than strictly necessary is that I rarely use shorthand for groups of characters. For example the tool might have a shorthand for digit but I always write [0-9] when I need to match a digit. Also probably because the shorthand might or might not be different for different tools.

Regexes are also known to be “write once read never”, in that writing a regex is relatively easy, but revisiting a semi-complicated regex you or someone else wrote in the past takes a little bit of extra effort to figure out what it’s matching and what edits one should make to it. In this case, tools like https://regex101.com/ or https://www.debuggex.com/ help a lot.

nuancebydefault

The problem with escaping (like with using quotes) is often that you need to know through how many parsers the string goes. The shell or editor, the language you are programming in and the regexp engine each time can strip off an escape character or a set of outer quotes. That and of course different dialects of regexp makes things complicated.

mystified5016

No one doubts the power or utility of regexes or ffmpeg, but they are both complicated beasts that really take a lot of skill.

They're both tools where if they're part of your daily workflow you'll get immense value out of learning them thoroughly. If instead you need a regex once or twice a week, the benefit is not greater than the cost of learning to do it myself. I have a hundred other equally complicated things to learn and remember, half the job of the computer is to know things I can't put in my brain. If it can do the regex for me, I suddenly get 70% of the value at no cost.

Regex is not a tool I need often enough to justify the hours and brain space. But it is still an indespensible tool. So when I need a regex, I either ask a human wizard I know, or now I ask my computer directly.

imp0cat

It's self-reinforcing though. If you invest the time to learn, then you may find yourself (i a beafutiful house :)) using it a lot more than two times a week.

nuancebydefault

I think this way of thinking is an uphill battle.

My kid uses wifi, google classroom tools, youtube, games,... I can tell him if only you knew command.com, ipconfig, doom.wad formats, lateg,... you could be so much more proficient. I already know this will never happen, just like I never learned x86 assembly.

The same goes for tools like LLMs, once you are used to them, your knowledge shifts.

skydhash

I learned a bit of assembly and it was a god send to understand linkers and how FFI works. Also make it easier to have a good model on using a debugger. Not that useful on a tactical level, but really great when faced with some errors in your compiled programs.

earnestinger

Not sure about ffmpeg, but you should definitely try memorising regexp. Casual Search&replace that becomes possible is worth it.

sergiotapia

in 15 years it never sticks and by the time i need it again i've forgotten it! :D

kevin_thibedeau

Don't learn the Perl influenced extensions. You just need POSIX EREs (and BREs for some older utilities) which are simple enough to keep in the head.

ziml77

And with the POSIX EREs, everything except the syntax for character classes will carry over to other common Regex dialects.

Over2Chars

I'll just leave this here

"The Insanity Of Linux's Regular Expressions " https://www.youtube.com/watch?v=ys7yUyyQA-Y

earnestinger

Many loosely compatible (so, not compatible if we are strict..) implementations are a problem, but awareness and testing helps.

All in all, my life would be miserable if I would not have regexp available in grep/sed/editor/ide/java/python, their usefulness trump any such inconveniences.

jmb99

For me, it wasn’t so much learning ffmpeg, as it was understanding containers/codecs/encoders/streams/etc. Learning all of the intricacies there made ffmpeg make a lot more sense.

skydhash

Almost no one cares to understand the domain of the tool anymore, they only want result and expect a simplified interface that already does the unique thing they want to do, but can’t accept that a power tool can only be used with training.

teaearlgraycold

Gotta be honest, years of configuring automod on Reddit have honed me into a regex God.

shlomo_z

... Then ChatGPT came along and I had 3 problems! https://regex.info/blog/2006-09-15/247

hackingonempty

CSS has entered the ChatGPT.

kccqzy

My rule for using LLMs is that anything that's one off is okay. Anything that's more permanent and committed to a repo needs a human review. I strongly suggest you have an understanding of the basics (at least the box model) so that you are competent at reviewing CSS code before using LLM for that.

permo-w

I've been looking for a good guide on prompting LLMs for CSS.

does anyone know of any?

johnisgood

I have no set of rules when prompting LLMs for CSS, it does seem to work more or less for me though.

What are your current issues or what limitations have you ran into?

jjcm

In addition to the many others mentioned, here's a script I just threw together that simplifies a lot of these chained commands - llmpeg: https://github.com/jjcm/llmpeg

If you have ffmpeg installed and an OpenAI env api key set, it should work out of the box.

Demo: https://image.non.io/1c7a92ef-0917-49ef-9460-6298c7a9116c.we...

juancroldan

Same here, it's one of these things where AI has taken over completely and I'm just a broker that copy-pastes error traces.

magarnicle

My experience got even better once I learned how complex filters worked.

dylan604

learning how to use splits to do multiple things all in one command is a god send. the savings of only needed to read the source and convert to baseband video once is a great savings.

i started with avisynth, and it took time for my brain to switch to ffmpeg. i don't know how i could function without ffmpeg at this point

nine_k

I do it the old way: I write down the commands as a shell script, and reuse later.

But really what ffmpeg is missing is an expressive language to describe its operation. Something well-structured, like what jq does for JSON.

skydhash

It already does. It’s the cli flags. What you’re missing is the semantic which you can get with learning about containers, codecs, and other stuff. You don’t use grep and sed with no understanding of what a text file is.

NetOpWibby

Truly, a net positive to my life. Just a few days ago I asked my AI buddy (Claude) to create a zsh script to organize my downloads folder according to the Johnny Decimal system. I’ve since modified it to move the files to a JD setup on my desktop.

The sense of elation I get when I wonder aloud to my digital friend and they generate what I thought was too much to expect. Well worth the subscription.

pdyc

I ended up creating my own tool to generate ffmpeg commands https://newbeelearn.com/tools/videoeditor/

bambax

Basic syntax for re-encoding a video file did take me some time to memorize, but isn't in fact too hard:

  ffmpeg <Input file(s)> <Codec(s)> <MAPping of streams> <Video Filters> output_file

- input file: -i, can be repeated for multiple input files, like so:

  ffmpeg -i file1.mp4 -i file2.mkv

If there is more than one input file then some mapping is needed to decide what goes out in the output file.

- codec: -c:x where x is the type of codec (v: video, a: audio or s:subtitles), followed by its name, like so:

  -c:v libx265

I usually never set the audio codec as the guesses made by ffmpeg, based on output file type, are always right (in my experience), but deciding the video codec is useful, and so is the subtitles codec, as not all containers (file formats) support all codecs; mkv is the most flexible for subtitles codecs.

- mapping of streams: -map <input_file>:<stream_type>:<order>, like so:

  -map 0:v:0 -map 1:a:1 -map 1:a:0 -map 1:s:4

Map tells ffmpeg what stream from the input files to put in the output file. The first number is the position of the input file in the command, so if we're following the same example as above, '0' would be 'file1.mp4' and '1' would be 'file2.mkv'. The parameter in the middle is the stream type (v for video, a for audio, s for subtitles). The last number is the position of the stream IN THE INPUT FILE (NOT in the output file).

The position of the stream in the output file is determined by the position of the map command in the command line, so for example in the command above we are inverting the position of the audio streams (taken from 'file2.mkv'), as audio stream 1 will be in first position in the output file, and audio stream 0 (the first in the second input file) will be in second position in the output file.

This map thing is for me the most counter-intuitive because it's unusual for a CLI to be order-dependent. But, well, it is.

- video filters: -vf

Video filters can be extremely complex and I don't pretend to know how to use them by heart. But one simple video filter that I use often is 'scale', for resizing a video:

  -vf scale=<width>:<height>

width and height can be exact values in pixels, or one of them can be '-1' and then ffmpeg computes it based on the current aspect ratio and the other provided value, like this for example:

  -vf scale=320:-1

This doesn't always work because the computed value should be an even integer; if it's not, ffmpeg will raise an error and tell you why; then you can replace the -1 with the nearest even integer (I wonder why it can't do that by itself, but apparently, it can't).

And that's about it! ffmpeg options are immense, but this gets me through 90% of my video encoding needs, without looking at a manual or ask an LLM. (The only other options I use often are -ss and -t for start time and duration, to time-crop a video.)

izacus

> This doesn't always work because the computed value should be an even integer; if it's not, ffmpeg will raise an error and tell you why; then you can replace the -1 with the nearest even integer (I wonder why it can't do that by itself, but apparently, it can't).

It's not about integer, but some of the sizes need to be even. You can use `-vf scale=320:-2` to ensure that.

bambax

It's hard for a number to be even without first being an integer, no? ;-)

But thanks for '-2', didn't know about that! It's the exact default option I needed! Will be using that always from now on.

https://stackoverflow.com/questions/71092347/ffmeg-option-sc...

jmb99

> then you can replace the -1 with the nearest even integer (I wonder why it can't do that by itself, but apparently, it can't).

Likely because the aspect ratio will no longer be the same. There will either be lost information (cropping), compression/stretching, or black bars, none of which should be default behaviour. Hence, the warning.

Over2Chars

I think you're onto something. I've had hit or miss experiences with code from LLMs but it definitely makes the searching part different.

I had a problem I'd been thinking about for some time and I thought "Ill have some LLM give me an answer" and it did - it was wrong and didn't work but it got me to thinking about the problem in a slightly different way and my quacks after that got me an exact solution to this problem.

So I'm willing to give the AI more than partial credit.

sathishvj

I would like to throw in a tool that I built into the ring: gencmd - https://gencmd.com/. There is a web version and also a CLI version.

If the CLI is installed, you can do: gencmd -c ffmpeg extract first 1 minute of video

Or you can just search for the same in the browser page.

archerx

Why not just use Handbrake? It’s just FFMpeg but with a GUI.

wildzzz

That's fine for encoding but Handbrake doesn't let you do video streaming to my knowledge.

urda

For me it was using a container of it, instead of having to install all the things FFmpeg needs on a machine.

skirge

llm - Clippit of 202x, but for the original Pentium was enough.

latexr

I thought this was going to be a website managed by an experienced user of FFmpeg sharing from their collection of accumulated knowledge, but then was immediately disappointed on the first example I clicked on.

https://www.ffmpegbyexample.com/examples/l1bilxyl/get_the_du...

Don’t call two extra tools to do string processing, that is insane. FFprobe is perfectly capable of giving you just the duration (or whatever) on its own:

  ffprobe -loglevel quiet -output_format csv=p=0 -show_entries format=duration video.mp4

Don’t simply stop at the first thing that works; once it does think to yourself if maybe there is a way to improve it.

gariany

Hi, original poster here. I think calling it "insane" is a bit of an exaggeration lol. Don't you think?

I like your solution better!

latexr

> I think calling it "insane" is a bit of an exaggeration

Yes, I agree. It was decidedly the wrong word to use and the post would undoubtedly have been better without that part. Unfortunately, the edit window had already passed by the time I reread it.

jazzyjackson

This reminds me I need to publish my write up on how I've been converting digitized home video tapes into clips using scene detection, but in case anyone is googling for it, here's a gist I landed on that does a good job of it [0] but sometimes it's fooled by e.g. camera flashes or camera shake so I need to give it a start and end file and have ffmpeg concatenate them back together [1]

Weird thing is I got better performance without "-c:v h264_videotoolbox" on latest Mac update, maybe some performance regression in Sequoia? I don't know. The equivalent flag for my windows machine with Nvidia GPU is "-c:v h264_nvenc" . I wonder why ffmpeg doesn't just auto detect this? I get about 8x performance boost from this. Probably the one time I actually earned my salary at work was when we were about to pay out the nose for more cloud servers with GPU to process video when I noticed the version of ffmpeg that came installed on the machines was compiled without GPU acceleration !

[0] https://gist.githubusercontent.com/nielsbom/c86c504fa5fd61ae...

[1] https://gist.githubusercontent.com/jazzyjackson/bf9282df0a40...

jack_pp

> Probably the one time I actually earned my salary at work was when we were about to pay out the nose for more cloud servers with GPU to process video when I noticed the version of ffmpeg that came installed on the machines was compiled without GPU acceleration !

Issue with cloud CPU's is that they don't come with any of the consumer grade CPU built-in hardware video encoders so you'll have to go with the GPU machines that cost so much more. To be honest I haven't tried using HW accel in the cloud to have a proper price comparison, are you saying you did it and it was worth it?

jazzyjackson

We were a quick and dirty R&D team that had to do a lot of video processing quickly, we were not very cost sensitive and didn’t have anything other than AWS to work with, so I can’t speak to whether it was worth it :)

radicality

Are the hardware encoders even good? I thought that unless you need something realtime, it's always better to spend the cpu cycles on a better encode with th software encoder. Or have things changed ?

jmb99

They still suck compared to software encoders. This is true for both H.264 and H.265 on AMD, Nvidia, and Intel GPUs. They’re “good enough” for live streaming, or for things like Plex transcoding, or where you care only about encoding speed and have a large bandwidth budget. They’re better than they used to be, but not worth using for anything you really care about.

zos_kia

That's my experience too. I transcode a lot of video for a personal project and hardware acceleration isn't much faster. I figure that's because on CPU I can max out my 12 cores.

The file size is also problematic I've had hardware encodes twice as large as the same video encoded with CPU.

jazzyjackson

Thanks for that datapoint, I was a little bummed to see ffmpeg not using any of my Macs GPUs, but the CPUs ain’t no slouch so I’ll just go with software encoding on Mac

siscia

Would you, or anyone else, be interested in ffmpeg in the cloud?

Connect credit card, open a web UI, send the command, the files, and eventually get the output?

zos_kia

I would SO love it ! I regularly take a look at the existing offerings, and there's a few options for "transcode video as API". However it's pretty costly, i regularly have batches of videos that would set me back 30 to 80 bucks if i were to transcode them in the cloud. I don't think it can be done at any price point i'd be happy with for this kind of personal project - especially considering that the alternative is just to max out my CPU for a day or two.

jack_pp

I know they used to be worse, haven't tested the newest ones

dekhn

I used ffmpeg for empty scene detection- I have a camera pointed at the flight path for SFO, and stripped out all the frames that didn't have motion in them. You end up with a continuous movie of planes passing through, with none of the boring bits.

hnuser123456

Then can you merge all the clips starting when motion starts and see hundreds of planes fly across at once?

dekhn

Interesting. Yes, I assume that's possible although I'm not sure how you handle the background- I guess you find an empty frame, and subtract that from every image with a plane.

One of the advantages of working with image data is that movies are really just 3d data and as long as all the movies you work with are the same size, if you have enough ram, or use dask, you could basically do this in a couple lines of numpy.

hnuser123456

You could do an add operation if the background is dark enough, or yeah, take a local sample of the background to subtract from each clip, and choose a specific background...

rahimnathwani

  -c:v h264_nvenc

This is useful for batch encoding, when you're encoding a lot of different videos at once, because you can get better encoding throughput.

But in my limited experiments a while back, I found the output quality to be slightly worse than with libx264. I don't know if there's a way around it, but I'm not the only one who had that experience.

ziml77

IIRC they have improved the hardware encoder over the generations of cards, but yes NVENC has worse quality than libx264. NVENC is really meant for running the compression in real-time with minimal performance impact to the system. Basically for recording/streaming games.

icelancer

So counterintuitive that nvenc confers worse quality than QSV/x264 variants, but it is both in theory and in my testing as well.

But for multiple streams or speed requirements, nvenc is the only way to fly.

xnx

Co-signing. Encode time was faster with nvenc, but quality was noticeably worse even to my untrained eye.

jazzyjackson

Fascinating, it didn't occur to me quality could take a hit, I thought the flag merely meant "perform h264 encoding over here"

Edit: relevant docs from ffmpeg, they back up your perception, and now I'm left to wonder how much I want to learn about profiles in order to cut up these videos. I suppose I'll run an overnight job to reencode them from Avi to h264 at high quality, and make sure the scene detect script is only doing copys, not reencoding, since that's the part I'm doing interactively, there's no real reason I should be sitting at the computer while its transcoding.

Hardware encoders typically generate output of significantly lower quality than good software encoders like x264, but are generally faster and do not use much CPU resource. (That is, they require a higher bitrate to make output with the same perceptual quality, or they make output with a lower perceptual quality at the same bitrate.)

[0] https://trac.ffmpeg.org/wiki/HWAccelIntro

norgie

Cutting videos with copy can result in some weird playback issues if the cuts aren't on keyframes.

For manually cutting up videos, I use LosslessCut, which I think uses ffmpeg under the hood and is really helpful for finding and cutting on keyframes.

throwaway4PP

It’s crude, but you can overcome the degraded quality imparted by gpu accelerated encoding by specifying a higher video bitrate.

Find a complex short scene in your cpu encoded video, extract it, ffprobe it to get average video bitrate, and take the same clip in raw and try gpu accelerated encoding at +20% bitrate. From there, iterate.

For a friend’s use-case that I helped with, +30% video bitrate bump overcame the degraded vquality.

Edit: strangely enough, if memory serves, after the correcting +30% was applied the actual ffprobe bitrates between the videos were very similar, maybe a 10% or less difference. Someone smarter than me can work that logic out.

pertymcpert

Yes. The reason is that there's many ways to encode a video, you can choose to spend a lot of compute in order to get the best quality, or the best size efficiency. Fixed function hardware encoders by nature have much less freedom in how they encode, and additionally are expected to be faster, or even real time.

dekhn

I've gotten pretty good at various bits of ffmpeg over time. Its CLI has a certain logic to it... it's order dependent (not all unix CLIs are).

Lately, I've been playing around with more esoteric functionality. For example, storing raw video straight off a video camera on a fairly slow machine. I built a microscope and it reads frames off the camera at 120FPS in raw video format (YUYV 1280x720) which is voluminous if you save it directly to disk (gigs per minute). Disks are cheap but that seemed wasteful, so I was curious about various close-to-lossless techniques to store the exact images, but compressed quickly. I've noticed that RGB24 conversion in ffmpeg is extremely slow, so instead after playing around with the command line I ended up with:

  ffmpeg -f rawvideo -pix_fmt yuyv422 -s 1280x720 -i test.raw  -vcodec libx264 -pix_fmt yuv420p  movie.mp4 -crf 13 -y

This reads in raw video- because raw video doesn't have a container, it lacks metadata like "pixel format" and "image size", so I have to provide those. It's order dependent- everything before "-i test.raw" is for decoding the input, and everythign after is for writing the output. I do one tiny pixel format conversion (that ffmpeg can do really fast) and then write the data out in a very, very close to lossless format with a container (I've found .mkv to be the best container in most cases).

Because I hate command lines, I ended up using ffmpeg-python which composes the command line from this:

  self.process = (
            ffmpeg.
            input(
                "pipe:",
                format="rawvideo",
                pix_fmt="yuyv422",
                s="{}x{}".format(1280, 720),
                threads=8
            )
            .output(
                fname, pix_fmt="yuv422p", vcodec="libx264", crf=13 
            )  
            .overwrite_output()
            .global_args("-threads", "8")
            .run_async(pipe_stdin=True)
            )

and then I literally write() my frames into the stdin of that process. I had to limit the number of threads because the machine has 12 cores and uses at least 2 at all times to run the microscope.

I'm still looking for better/faster lossless YUV encoding.

zahlman

>Its CLI has a certain logic to it... it's order dependent (not all unix CLIs are).

Which is appropriate. A Unix pipeline is dependent on the order of the components, and complex FFMpeg invocations entail doing something analogous.

>I ended up using ffmpeg-python which composes the command line from this

A lot of people like this aesthetic, but doing "fluent" interfaces like this is often considered un-Pythonic. (My understanding is that ffmpeg-python is designed to mirror the command-line order closely.) The preference (reinforced by the design of the standard library and built-in types) is to have strong https://en.wikipedia.org/wiki/Command%E2%80%93query_separati... . By this principle, it would look something more like

  ffmpeg(global_args=..., overwrite_output=True).process_async(piped_input(...), output(...))

where using a separate construction process for the input produces a different runtime type, which also cues the processing code that it needs to read from stdin.

dekhn

To be honest what I really wanted is more like a programming API or config file than attempting to express complex pipelines and filters in a single command line.

As for what's unpythonic: don't care. My applications has code horrors that even Senior Fellows cannot unsee.

zahlman

I get that. My critique is for the library authors, not you.

Ch00k

Similar, arguably simpler, Python library that provides an interface to FFmpeg command line is ffmpy [0], of which I am the author.

[0] https://github.com/Ch00k/ffmpy

jcalvinowens

> I'm still looking for better/faster lossless YUV encoding.

Look no further: https://trac.ffmpeg.org/wiki/Encode/FFV1

dekhn

I spent some time with this on my data set, and in my hands I wasn't able to produce results that were convincingly better than libx264, but with slower encodes and larger output files. It's really hard to beat libx264.

jcalvinowens

>> I'm still looking for better/faster lossless YUV encoding.

> I wasn't able to produce results that were convincingly better than libx264

With "-qp 0"? Otherwise, it's not a valid comparison... "-crf 13" is nowhere near lossless (though it might appear so visually).

FFV1 is much better than H264 at lossless compression in my experience. Here's a random sample of a ten second 4K input I had handy (5.5G uncompressed):

    h264-ultrafast    1.951s   850M
    h264-veryslow    46.528s   715M
    ffv1              8.883s   637M

But yeah, if you don't actually require truly lossless data, it's a huge waste.

at_a_remove

I am here to sell you on one word: ramdisks.

If you are doing processing with intermediate steps you do not want to keep? Ramdisks. Oh yeah. Oh yeah.

Moru

This seems to be very forgotten tech. First time I used that was to load NetHack to ram instead of the slow diskette on my Atari. Now I still use it as webcache for work to not bother the database with so many requests.

When I set up the server, the ramdisk didn't have a way of shrinking when space wasn't needed so had to make sure it doesn't eat up all memory when growing unlimited. I bet it's smarter nowadays.

nickdothutton

FFmpeg is one of those tools I need to use so infrequently that he exact syntax never seems to stick. I've resorted to using an LLM to give me the command line I need. The only other tool that I ever had trouble with was 1990s-era MegaCLI from LSI Logic, also something I barely used from one year to the next (but one where you really need to get it right under pressure).

pseudosavant

I've been using FFMPEG for 15+ years, and still can't remember almost any commands. LLMs have been amazing for using FFMPEG though. ChatGPT and Claude do wonders with "give me an ffmpeg command that will remux a video into mkv, include subtitle.srt in the file, and I only want it between 0:00:05 and 0:01:00." It produced this in case you were wondering: `ffmpeg -i input.mp4 -i subtitle.srt -ss 00:00:05 -to 00:01:00 -map 0 -map 1 -c copy -c:s mov_text output.mkv`

I wonder how small of an LLM you could develop if you only wanted to target creating ffmpeg commands. Perhaps it could be small enough to be hosted on a static webpage where it is run locally?

porterde

Perhaps small enough to include in ffmpeg itself so you can just write commands `ffmpeg do this thing I want`.

Now I say this, it seems like there should already be a shell that is also an LLM where you can mix bits of commands you vaguely remember and natural language a bit like Del Boy speaking French...

pseudosavant

That would be an amazingly useful feature of ffmpeg, and considering how large its dependencies are (390MB of packages for `apt install ffmpeg` on a fresh Raspberry Pi OS install), it would be reasonable to have an optional model package.

Alex-Programs

Warp terminal does that. It's cool.

sitkack

https://github.com/warpdotdev/Warp

https://www.warp.dev/blog/how-warp-works

Warp terminal – no more login required (49 days ago) https://news.ycombinator.com/item?id=42247583

Show HN Warp.dev (3 years ago) https://news.ycombinator.com/item?id=30921231

Show HN llmterm https://news.ycombinator.com/item?id=42498901 https://github.com/timschmidt/llmterm

7jjjjjjj

-c:s mov_text is unnecessary and in fact might be fucking things up

escapecharacter

I've just maintained my own note doc, going on 15 years now, of my most commonly used syntax. When that fails, I grep my bash history.

daveslash

Same. The only thing that sticks is converting from format X to .mp4. Everything else I need to look up every single time.

Relevant XKCD https://xkcd.com/1168/

dmd

Yeah I commented the other day, tongue firmly in cheek, that it's probably worth burning down all the rainforests just so LLMs can tell me the right ffmpeg flags to do what I want.

fastily

Nice! This reminds me of my own ffmpeg cheatsheet; I would imagine that everyone who uses ffmpeg frequently has a similar set of notes

https://github.com/fastily/cheatsheet/blob/master/ffmpeg.md

efortis

FWIW, mine: https://github.com/ericfortis/quick-reference/blob/main/ffmp...

joshbaptiste

One thing on Linux systems I like to do is build ffmpeg statically.. as distro versions are sometimes too old or don't include modules I prefer.. this containerized version has done wonders for me https://github.com/wader/static-ffmpeg

greenavocado

Don't forget that Gstreamer exists and its command line and documentation make a little bit more sense than ffmpeg because GStreamer is pipeline based and the composition is a little bit more sane. I stopped using ffmpeg entirely and only use GStreamer for intense video work.

jack_pp

Gstreamer can give you more control and has friendlier API's if you're gonna make a pipeline programatically but for one off stuff ffmpeg seems much friendlier to me. For example it has sane x264 defaults while with gst-launch you have to really know what you're doing to get quality x264 encoding

legends2k

I thought FFmpeg is pipeline based too; graph of filters. Am I missing something? You can set up a complex graph of source, sink and transform filters.

radicality

I wish there was some sort of local gui / tool to drag and drop nodes, connect them together, type-check the graph if possible, and it would only show the ffmpeg command to run which you could paste. Anyone know or anything?

pbmahol

see lavfi-preview on github. Its GUI app for libavfilter/FFmpeg filters

greenavocado

You're right, but gstreamer is a little bit more sane for many use cases. Maybe ffmpeg is more advanced; I am not sure. I find the pieces fit together better with gstreamer.

lehi

FFmpeg's filter DSL is so good that I get annoyed if I ever have to fall back to command line switches.

remram

GStreamer feels like abandonware though, they also got big vulnerabilities recently, and their docs are very defunct.

greenavocado

Not sure about the vulns but I am actively discussing things with the devs on their Matrix

LocalPCGuy

I was excited to see this as just last night I was using FFmpeg to combine digital (legally owned) movies with multiple parts into a single MKV file. It worked great, the one thing (and this is undoubtedly just a knowledge problem on my part), is I could not get it to copy/include subtitles from both parts. I have a feeling I might need to extract the subtitle files and combine them and then re-include the combined version, but was hoping there would be a solution in this site for doing something like that. Unfortunately, I didn't even see the combine as one of the examples.

For reference:

One-liner:

> ffmpeg -loglevel info -f concat -safe 0 -i <(for f in *.mkv; do echo "file '$(pwd)/$f"; done) -c copy output.mkv

Or the method I ended up using, create a files.txt file with each file listed[0]

> ffmpeg -f concat -safe 0 -i files.txt -c copy output.mkv

files.txt

> file 'file 1.mkv' > file 'file 2.mkv' > # list any additional files

0: https://ma.ttias.be/use-ffmpeg-combine-multiple-videos/

gariany

This will fail on most inputs

AdieuToLogic

Here is the GitHub repo for a ffmpeg book which may be a nice supplement to this site:

https://github.com/jdriselvato/FFmpeg-For-Beginners-Ebook

Narciss

Oh this is nice, thank you!

merksoftworks

ffmpeg has always felt like a gui application crammed into tui format. I've had the displeasure of using the C api a few times, while it's straight forward in many respects, it makes invalid states extremely easy to represent. I would love a realtime AV1 encoding framework that "just works".

jmb99

> ffmpeg has always felt like a gui application crammed into tui format.

It’s one of the only tools where I reach for a GUI equivalent (Handbrake) by default, unless I’m doing batch processing. There are a few pure ffmpeg GUIs out there as well. There’s just something about working with video that CLI doesn’t work right with my brain for.

mastax

I can vouch for GStreamer as an API. I was using the Rust bindings so not super familiar with the C API but it looks good. GObject makes some things verbose but once you understand it you can interact with every object in the API consistently. There is a ton of necessary complexity (video is hard) but it’s really well designed and pretty well implemented and documented.

If you have a pretty normal use case the Bins (decodebin, transcodebin, playbin) make that pretty easy. If you have a more complex use case the flexibility of the design makes it possible.

garaetjjte

ffmpeg API is somewhat clunky but it works fine. I dread working with gstreamer, sea of leaky abstractions, inexplicable workarounds and mysterious bugs.

tiborsaas

I like this insight, but TUI is something graphical while ffmpeg is just CLI.

It would be cool to see if a TUI tool existed. Something like https://github.com/Twinklebear/fbed but more feature complete.

franze

I love using FFMpeg via Wasm for ... senseless ... mini projects i.e.: https://video-2-sprites.franzai.com/ Video 2 Sprites Converter - totally over-engineered

dsp_person

Love the bouncing progress bar. Also nice ffmpeg wasm only 11MB

alpb

I love "X by Example" sites! But if you don't work with a tool like ffmpeg imagemagick day in and out, there's no way you'll remember their unintuitive syntax or will want to spend the time to get your one-time job done. I'd still probably not use this site to scan a dozen of examples and try to put together the pieces of the puzzle; instead, I'd probably just use an LLM who already scanned the entire web corpus and can probably get me to a solution faster, right? At that point, I wonder what folks get out of this site?

gariany

Its for when people google how do I do X. Also, I've built this site before chatgpt was a thing...

peter_retief

"Print a text file to STDOUT using ffmpeg" ffmpeg -v quiet -f data -i input.txt -map 0:0 -c text -f data - I tried this in a directory with input.txt with some random text Nothing.

So changed the verbosity to trace ffmpeg -v trace -f data -i input.txt -map 0:0 -c text -f data -

---snip-- [dost#0:0 @ 0x625775f0ba80] Encoder 'text' specified, but only '-codec copy' supported for data streams [dost#0:0 @ 0x625775f0ba80] Error selecting an encoder Error opening output file -. Error opening output files: Function not implemented [AVIOContext @ 0x625775f09cc0] Statistics: 10 bytes read, 0 seeks

I was expecting text to be written to stdout? What did I miss?

Narushia

It's not working for me either, on FFmpeg 7.0.2. I suspect something has changed in FFmpeg since that command was shared on the Reddit post mentioned on the website. That was a few years ago.

However, from the same Reddit thread, this works:

ffmpeg -v quiet -f data -i input.txt -map 0 -f data pipe:1

EDIT: just verified the `-c text` approach works on FFmpeg major versions 4 and 5. From FFmpeg 6 onwards, it's broken. The `pipe:1` method works from FFmpeg 5 onwards, so the site should probably be updated to use that instead (also, FFmpeg 5.1 is an LTS release).

peter_retief

Thanks, yes they should update the site.

peter_retief

https://x.com/i/grok/share/rhb9niOru2tk17SdEqIhLvfhV

nuancebydefault

When I read that, it resembles very much the format of responses from copilot.microsoft.com

especially: point 4 is the final giveaway!

peter_retief

Ha, very literal answer, why not use cat to print the file, is that a bit of sarcasm creeping into the LLM's?

nuancebydefault

In fact, that LLMs are typically steered away from sarcasm or irony (i guess via system prompts stressing on formalism), makes it easier to identify their output. Its output is so formal, taking the question very seriously though it is obviously just an exercise, that it sounds ironical.

xenodium

I'm grateful for sites like this and these days LLMs too. ffmpeg is awesome, but I can never rememeber the right incantation. The sites/tools get me the right ffmpeg answer, but I still needed to remember the answer next time (or look things up again). Now I save them as reusable commands: https://lmno.lol/alvaro/how-i-batch-apply-and-save-one-liner...

patchtopic

also worthwhile consulting this resource: https://www.youtube.com/watch?v=9kaIXkImCAM

asicsp