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• How to segment audio and video to the same segments number ?

  24 décembre 2019, par julian zapata

  I’ve extracted audio and video from the same mp4 file and created different variants for different resolutions. When I segment the videos and the audio file with MP4Box, the video segments are the same segments number but the audio segments have one more. I need the video and audio segments to be the same number to use with dash.

  I’m using the next commands to produce the video and audio files :

  Command to extract the audio from mp4 file :

  ffmpeg -y -i "transformers.mp4" -c:a aac -b:a 192k -vn "transformers_audio.m4a"

  Produce each variant of the video with the next command modifying the resolution and bitrate parameters :

  ffmpeg -i transformers.mp4 -c:v libx264 -r 24 -x264opts "keyint=48:min-keyint=48:no-scenecut" -an -vf scale=640:360 -b:v 750k -dash 1 transformers_640x360_750k.mp4

  Generate the mpd file and segment the videos and audio each 4 seconds with :

  mp4box -dash 4000 -profile "dashavc264:live" -bs-switching no -sample-groups-traf \ 
  
  -out output4\ 
  
  transformers.mpd \ 
  
  transformers_480x270_400k.mp4 \ 
  
  transformers_640x360_800k.mp4 \ 
  
  transformers_960x540_1200k.mp4 \
  
  transformers_1280x720_1500k.mp4 \ 
  
  transformers_1920x1080_4000k.mp4 \
  
  transformers_audio.m4a

  This produces 36 segments for each variant of the video and 37 for the audio. How to solve this little variation ? How to make the audio segments number exactly the number of video segments ?

• FFmpeg option to generate a .m4s file every second

  29 janvier 2020, par Adrian Angkajaya

  I am trying to stream my live recording from a camera (web cam/ ip cam) to my web application. The streaming technique I use is MPEG-DASH, which has manifest in MPD format. To generate an MPD format from the web-cam, I use FFmpeg tool in shell command line :
  ffmpeg -re -y -f dshow -i video="Logitech HD Webcam C525" -c:v libx264 -c:a libfdk_aac -f dash "manifest.mpd". This code will generate a video chunk in .m4s format every 5-8 seconds.

  Question is, what FFmpeg option can I use to generate a .m4s file every second instead of every 5-8 seconds ? I suppose it has something to do with segment ?

• Mux ts segments to fragmented mp4 in realtime

  10 avril 2021, par bsack

  I have an HLS stream which plays in the browser. What I want to do is have a URL like /stream.mp4 that plays the livestream back as a fragmented mp4 from the current point in time. This way you could download the stream as a single file and it would work without any js dependencies.

  


  The method I thought of is :

  


  

  1. send an mp4 header

  


  2. wait for a new segment

  


  3. convert the segment into an mp4 fragment with ffmpeg

  


  4. send the mp4 fragment

  


  5. go to 2.

  


  


  (I know you can concatenate .ts segments but they don't play in Firefox.)

  


  This answer describes how to create a fragmented mp4 when you have all the segments at hand (tl ;dr use -movflags frag_keyframe+emptymoov). But I want to do this on the fly so each new HLS segment is converted to an mp4 fragment as soon as it's created.

  


  I think this is similar to what DASH does natively, where any chunk chunk-$n.m4s can be appended to init.m4s and it'll be a proper fragmented mp4. But can this be done without using DASH ?

  


  How can I transmux a ts segment into an mp4 fragment ?

  


  Edit : I found a way of doing what I wanted, but not through transmuxing mpegts segments to fmp4. It turns out that later versions of HLS do support fragmented mp4 (like DASH does), and FFmpeg provides the -hls_segment_type fmp4 option for this.