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• avformat/dump : Print stream start offsets for input streams

  23 février 2019, par softworkz

  avformat/dump : Print stream start offsets for input streams
  Seeing the offset of video and audio streams to each other is often
  
  a useful metric in diagnosing and understanding issues with playback
  
  or transcoding.
  
  This commit adds those offsets to the stream info print.
  Signed-off-by : softworkz <softworkz@hotmail.com>
  

  • [DH] libavformat/dump.c

• Start Android Java VM from native C code NDK (ffmpeg mediacodec use)

  19 avril 2021, par eusoubrasileiro

  I managed to cross-compile ffmpeg using the NDK for armv8a api 27 with MediaCodec hardware acceleration support.

  


  Using root after setting permissions, folders and setting properly LD_LIBRARY_PATH etc. I can run it without problems on a terminal session (ssh). Only if I don't try to use the -hwaccel option.

  


  If try to run something using -hwaccel, like :

  


  ffmpeg -rtsp_transport tcp -an -hwaccel mediacodec -c:v hevc_mediacodec -i rtsp://user:pass@192.168.0.100:554/onvif1 -f null - -benchmark


  


  I get the error bellow about No Java virtual machine.

  


  ...
Input #0, rtsp, from 'rtsp://user:pass@192.168.0.100:554/onvif1':
  Metadata:
    title           : H.265 Video, RtspServer_0.0.0.2
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: hevc (Main), yuv420p(tv, bt470bg), 1920x1080 [SAR 1:1 DAR 16:9], 10 fps, 10 tbr, 90k tbn, 10 tbc
    Stream #0:1: Audio: pcm_alaw, 8000 Hz, mono, s16, 64 kb/s
[amediaformat @ 0x7e2ea27300] No Java virtual machine has been registered
[hevc_mediacodec @ 0x7e2eb44f00] Failed to create media format
Stream mapping:
  Stream #0:0 -> #0:0 (hevc (hevc_mediacodec) -> wrapped_avframe (native))
Error while opening decoder for input stream #0:0 : Generic error in an external library


  


  Would it be possible to start (create or launch ?) the Dalvik Java VM directly from the C code ? I don't even know if those are correct terms. Make it visible for ffmpeg ?

  


  Any information that will help a Android Newbie get on his feet will be greatly appreciated. If that is possible I would write a little patch on the ffmpeg code.

  


  I really would not like to package this in an app only to be able to test around with this.

  


• ffmpeg : How to keep audio synced when doing many (100) cuts with filter select='between(t,start,stop)+between...'

  4 février 2021, par Louis

  I am cutting out silent parts of a 45 minute video (a lecture).
To do this, I use a filter to select, say one hundred, non-silent parts (I already know their start and end times).

  


  ffmpeg -i in.mp4
-vf "select='between(t,start_1,stop_1)+...+between(t,start_100,stop_100)', setpts=N/FRAME_RATE/TB"
-af "aselect='between(t,start_1,stop_1)+...+between(t,start_100,stop_100)', asetpts=N/SR/TB"
-c:a aac -c:v libx264 out.mp4


  


  It works, but at the end of the video the images are delayed relative to the audio.
After reading this answer I also added

  


  -shortest -avoid_negative_ts make_zero -fflags +genpts


  


  at the end of the command. It didn't help.

  


  As audio and video are concatenated independently I'm not surprised that tiny time errors due to finite frame rate add up.

  


  Is there a solution that doesn't involve saving every non-silent part as a file ?