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• ffmpeg to generate dash and HLS - best practise

  8 septembre 2017, par LaborC

  Looking for the correct way to encode a given input video in multiple bitrates and then package it for dash and HLS. I thought this is a basic task, but for me it was quite a challenge. So the way I do it is as follows :

  First I split my video (mp4) into video and audio (I encode the audio, because I need to make sure that the output codec is aac, which is a requirement for web I think).

  ffmpeg -c:v copy -an video_na.mp4 -i source_input.mp4
  
  ffmpeg -c:a aac -ac 2 -async 1 -vn audio.mp4 -i source_input.mp4

  Then I encode the video with the following commands :

      ffmpeg.exe -i video_na.mp4 -an -c:v libx264 -crf 18 \
  
  -preset fast -profile:v high -level 4.2 -b:v 2000k -minrate 2000k \
  
  -maxrate 2000k -bufsize 4000k -g 96 -keyint_min 96 -sc_threshold 0 \
  
  -filter:v "scale='trunc(oh*a/2)*2:576'" -movflags +faststart \
  
  -pix_fmt yuv420p -threads 4 -f mp4 video-2000k.mp4
  
  
  
      ffmpeg.exe -i video_na.mp4 -an -c:v libx264 -crf 18 \
  
  -preset fast -profile:v high -level 4.2 -b:v 1500k -minrate 1500k \
  
  -maxrate 1500k -bufsize 3000k -g 96 -keyint_min 96 -sc_threshold 0 \
  
  -filter:v "scale='trunc(oh*a/2)*2:480'" -movflags +faststart \
  
  -pix_fmt yuv420p -threads 4 -f mp4 video-1500k.mp4

  After that I fragment the videos (I used the parameter —timescale 10000 but then the result was out of sync).
  Sidenote : the -g parameter is 4 times 24 (frames). this is important because the fragmentation is 4000 (4 seconds)

  mp4fragment --fragment-duration 4000 video-2000k.mp4 \
  
  video-2000k-f.mp4
  
  
  
  mp4fragment --fragment-duration 4000 video-1500k.mp4 \
  
  video-1500k-f.mp4

  And finally package everything together again for dash (I used to use —use-segment-timeline but then again the result was out-of-sync).
  I use mp4dash and not mp4box because I want to be able to encrypt everything later on for DRM.

  mp4dash --media-prefix=out  \
  
        video-2000k-f.mp4  \
  
        video-1500k-f.mp4  \
  
       --out dash

  The result works in Firefox, Chrome, IE Edge via a webserver and via Cloudfront AWS Streaming also on older browsers.

  So for me there are still 2 tasks to accomplish.
  First I need to generate a HLS package for Apple Phone, IPad Users.
  And second : I need to encrypt everything.

  So far my HLS command is :

  ffmpeg -y -loglevel info ^
  
          -i video-2000k.mp4 \
  
          -i video-1500k.mp4 \
  
          -i audio.mp4 \
  
          -profile:v baseline -start_number 0 -hls_time 10 \
  
          -flags -global_header -hls_list_size 0 -f hls hls/master.m3u8

  This basically works, but generates only 1 bandwith without the posibility of multi-streams.
  I am not certain about that statement, but it looks that way.
  Has anyone an idea on what I am doing wrong ?

• lavf/dashenc : Add DASH segment type auto and make it the default

  17 novembre 2018, par Andrey Semashev

  lavf/dashenc : Add DASH segment type auto and make it the default
  This commit restores the ability to create DASH streams with codecs
  
  that require different containers that was lost after commit
  
  2efdbf7367989cf9d296c25fa3d2aff8d6e25fdd. It adds a new "auto" value for
  
  the dash_segment_type option and makes it the default. When in this mode,
  
  the segment format will be chosen based on the codec used in the stream :
  
  webm for Vorbis, Opus, VP8 or VP9, mp4 otherwise.
  

  • [DH] doc/muxers.texi
  • [DH] libavformat/dashenc.c

• avformat/matroskadec : Fix memleaks in WebM DASH manifest demuxer

  13 juin 2020, par Andreas Rheinhardt

  avformat/matroskadec : Fix memleaks in WebM DASH manifest demuxer
  In certain error scenarios, the underlying Matroska demuxer was not
  
  properly closed, causing leaks.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c