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• FFmpeg - How to choose video stream based on resolution

  23 septembre 2023, par Sylven

  I want to choose the video stream based on it's quality, let's say I want to choose one video stream with certain resolution.

  


  Manually selecting the video stream is not good enough for me because I want to process many files in bulk and they have the video streams in different order, so always going for certain position would make me end up with different resolutions.

  


  I don't want to use filters as that would make me reencode which I don't need and would make it way slower.

  


  I've tried using the -map with metadata but the only key that is different is "variant_bitrate" which has slightly different values everytime, so unless I can use some wildcard or conditionals, I guess it won't work either.

  


  What I want to try now is to obtain the exact bitrate of the stream using ffmpeg or ffprobe and then pass it to the ffmpeg command so it ends in something like this :

  


  ffmpeg -i <url> -map m:variant_bitrate:1760000 ...</url>

  


  PD : I've been reading the FFmpeg documentation and browsing the whole internet without luck.

  


  Edit :
I managed to make it work by first using ffprobe to obtain stream info in json format (easier to parse), then I search for the string "height": 540 and extract next 50 lines (counted them manually so I'm sure I'll pick the value I need), then I search for the string variant_bitrate and then I use a regular expression to extract the bitrate. Once I have the bitrate I make use of the MacOS clipboard (with pbcopy and pbpaste) to pass the value to the final ffmpeg command through the -map option using a metadata selector.

  


  ffprobe -v error -show_streams -of json "https://streamlink.com/master.m3u8?f=dash"
| grep -A 50 '"height": 540' 
| grep variant_bitrate
| grep -oe '\([0-9.]*\)' 
| pbcopy
&& ffmpeg -protocol_whitelist file,http,https,tcp,tls,crypto -i "https://streamlink.com/master.m3u8?f=dash" -map "0:a:0" -map "m:variant_bitrate:$(pbpaste)" -c copy "Output.mp4"


  


  (added line breaks for readability)

  


  I know it looks kinda dirty but I didn't find any other way to achieve my requirement.

  


• xcbgrab : XCB-based screen capture

  24 août 2014, par Luca Barbato

  xcbgrab : XCB-based screen capture
  Matches the x11grab screen capture by features.
  

  • [DBH] Changelog
  • [DBH] configure
  • [DBH] libavdevice/Makefile
  • [DBH] libavdevice/alldevices.c
  • [DBH] libavdevice/version.h
  • [DBH] libavdevice/xcbgrab.c

• lavc/hevcdec : output RASL frames based on the value of no_rasl_output_flag

  1er juin 2024, par Anton Khirnov

  lavc/hevcdec : output RASL frames based on the value of no_rasl_output_flag
  Instead of an ad-hoc scheme. Also, combine skipping RASL frames with
  
  skip_frame handling - current code seems flawed as it only executes for
  
  the first slice of a RASL frame and unnecessarily unsets is_decoded,
  
  which should not be set at this point anyway..
  Some RASL frames in fate-hevc-afd-tc-sei that were previously discarded
  
  are now output.
  

  • [DH] libavcodec/hevc/hevcdec.c
  • [DH] libavcodec/hevc/hevcdec.h
  • [DH] tests/ref/fate/hevc-afd-tc-sei