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• Save .mp4 from YouTube output stream

  15 mai 2023, par walolinux

  I am currently running a Ffmpeg script in Raspbian which works fine. It captures video from an USB webcam and stream it to YouTube.

  


  ffmpeg -thread_queue_size 512 -f v4l2 -video_size 1920x1080 -i /dev/video0 -ar 44100 -ac 2 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero -acodec aac -ab 128k -strict experimental -aspect 16:9 -vcodec h264 -preset veryfast -crf 25 -pix_fmt yuv420p -g 60 -vb 820k -maxrate 820k -bufsize 820k -profile:v baseline -r 30 -f flv rtmp://a.rtmp.youtube.com/live2/XXX-XXX-XXX


  


  But I also want to save the file into an mp4 file.

  


  I have tried adding a .mp4 file to the end, but it generates a corrupt file and the stream does not emit at 1x speed, it get slower to 0.4x

  


  ffmpeg -thread_queue_size 512 -f v4l2 -video_size 1920x1080 -i /dev/video0 -ar 44100 -ac 2 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero -acodec aac -ab 128k -strict experimental -aspect 16:9 -vcodec h264 -preset veryfast -crf 25 -pix_fmt yuv420p -g 60 -vb 820k -maxrate 820k -bufsize 820k -profile:v baseline -r 30 -f flv rtmp://a.rtmp.youtube.com/live2/XXX-XXX-XXX output.mp4


  


  I have also tried without result :

  


  -vcodec copy -acodev copy output.mp4


  


  Any idea ? Thanks.

  


• Google’s YouTube Uses FFmpeg

  9 février 2011, par Multimedia Mike — General

  Controversy arose last week when Google accused Microsoft of stealing search engine results for their Bing search engine. It was a pretty novel sting operation and Google did a good job of visually illustrating their side of the story on their official blog.

  This reminds me of the fact that Google’s YouTube video hosting site uses FFmpeg for converting videos. Not that this is in the same league as the search engine shenanigans (it’s perfectly legit to use FFmpeg in this capacity, but to my knowledge, Google/YouTube has never confirmed FFmpeg usage), but I thought I would revisit this item and illustrate it with screenshots. This is not new information— I first empirically tested this fact 4 years ago. However, a lot of people wonder how exactly I can identify FFmpeg on the backend when I claim that I’ve written code that helps power YouTube.

  Short Answer
  How do I know YouTube uses FFmpeg to convert multimedia ? Because :

  1. FFmpeg can decode a number of impossibly obscure multimedia formats using code I wrote
  2. YouTube can transcode many of the same formats
  3. I screwed up when I wrote the code to support some of these weird formats
  4. My mistakes are still present when YouTube transcodes certain fringe formats

  Longer Answer (With Pictures !)
  Let’s take a video format named RoQ, developed by noted game designer Graeme Devine. Originated for use in the FMV-heavy game The 11th Hour, the format eventually found its way into the Quake 3 engine as well as many games derived from the same technology.

  Dr. Tim Ferguson reverse engineered the format (though it would later be open sourced along with the rest of the Q3 engine). I wrote a RoQ playback system for FFmpeg, and I messed up in doing so. I believe my coding error helps demonstrate the case I’m trying to make here.

  Observe what happened when I pushed the jk02.roq sample through YouTube in my original experiment 4 years ago :

  
  
  

  Do you see how the canyon walls bleed into the sky ? That’s not supposed to happen. FFmpeg doesn’t do that anymore but I was able to go back into the source code history to find when it did do that :

  
  
  

  Academic Answer
  FFmpeg fixed this bug in June of 2007 (thanks to Eric Lasota). The problem had to do with premature colorspace conversion in my original decoder.

  Leftovers
  I tried uploading the video again to see if the problem persists in YouTube’s transcoder. First bit of trivia : YouTube detects when you have uploaded the same video twice and rejects the subsequent attempts. So I created a double concatenation of the video and uploaded it. The problem is gone, illustrating that the backend is actually using a newer version of FFmpeg. This surprises me for somewhat esoteric reasons.

  Here’s another interesting bit of trivia for those who don’t do a lot of YouTube uploading— YouTube reports format details when you upload a video :

  
  
  

  So, yep, RoQ format. And you can wager that this will prompt me to go back through the litany of unusual formats that FFmpeg supports to see how YouTube responds.

• FFMPEG - Creating multiple copies of a video with different audio channels. Can't hear channel 4

  13 février 2020, par Gabriel_ris

  I’m working on a project where I need to have 6 copies of a video, where each copy only plays one audio channel.
  The original video has only 2 channel, with the same audio on each channel.
  First I had to copy one of the channels into the other 4 missing channels.
  I’m new to ffmpeg, I did some research and I used this command :

  ffmpeg -i input.mp4 -map_channel 0.1.0 -map_channel 0.1.0 -map_channel
  0.1.0 -map_channel 0.1.0 -map_channel 0.1.0 -map_channel 0.1.0 -c:v copy output.mp4

  That helped to turn the video into a 6 channels one. Then, I revised the command for each channel :

  ffmpeg -i input.mp4 -map_channel 0.1.0 -map_channel -1 -map_channel -1
  -map_channel -1 -map_channel -1 -map_channel -1 -c:v copy output_channel1.mp4

  ffmpeg -i input.mp4 -map_channel -1 -map_channel 0.1.0 -map_channel -1
  -map_channel -1 -map_channel -1 -map_channel -1 -c:v copy output_channel2.mp4

  and so on.

  All the videos worked perfectly on their own channels, but channel 4, in which I can only hear some low noise.
  I read channel 4 is used for low frequency audio in 5.1 configuration, which might be the problem.
  I tried specifying the channel layout to 6.0, increasing the volume, disabling guess_layout_max, but nothing worked.
  As I said, I’m new to ffmpeg, and probably there is a much better way to do it. I’d appreciate if someone here could help me.
  Thanks !