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• h.264 video in mp4 container jumps when played in VLC

  30 avril 2013, par Jayanth Nayak

  I have H.264 video and AAC audio generated in Andriod phone recieved wirelessly using SIP protocol and muxed using FFMPEG APIs, The generated mp4 when played through VLC or other player is never in Sync.
  when I see the time bar of Video, it skips after a certain duration.

  For example :
  in a video of 20s, the time bar seeks upto 14s properly, then it jumps to 18s and finishes at 20. The audio plays properly.

  I have following questions :

  1. Is PTS DTS calculations really required for muxing WITHOUT Encoding ? :

  we used

  PTS = (90000 * (1/FPS) * FrameNumber) - although this did not work :(

  currently FFMPEG is taking care of it internally.

  ---

  1. Why the video jumps ? is it because of less number of frames or wrong PTS values or something else ?

  ---

  1. For the following cases although There is jump, I am getting a good AV sync
     -15,20,25 FPS qCIF & AAC Audio

     But for 15 & 20 FPS of qVGA & VGA the audio lags by 0.5 seconds and for 25 FPS, the Video is just playing fast.
     thus why is there a delay for qVGA and VGA but not present for qCIF ? any dependency of Resolution on Time Stamp (PTS) calculation ??

     Analysis of 25 FPS Video showed that there are enough number of frames for 10s but the total time for the video shown by VLC is 14s. Why is this so ? and again, this video also jumps from 9s to 13s.

• AMR-NB support in javacv -> ffmpeg

  7 décembre 2013, par cyberpawn

  I am trying to use AMR_NB Codec in JavaCV Android but having problems :

  This is the code i run :

  avcodec.avcodec_register_all();
  
  avformat.av_register_all();
  
  AVCodec mCodec = avcodec.avcodec_find_encoder(avcodec.AV_CODEC_ID_AMR_NB);

  Output : The mCodec is null but if I pass avcodec.AV_CODEC_ID_AAC than mCodec is not null

  I am assuming that I have to recompile ffmpeg with —enable-libopencore-amrnb. So, I downloaded Android NDKr9+ffmpeg-2.0.2+last_stable_x264 and added them to javacv-cppjars folder, I have also installed opencore-amr library in /usr/local. In ffmpeg-2.0.2-android-arm.patch i added the —enable-libopencore-amrnb flag and run following command in terminal

  ANDROID_NDK=/Users/android-ndk-r9b/ FFMPEG_VERSION=2.0.2 ./build_ffmpeg-android-arm.sh

  The script runs but the libs are not generated and the jar is empty but if I remove the —enable-libopencore-amrnb flag back then the libs are generated successfully, Please advise what am I doing wrong ? What should I do ? Any help would be greatly appreciated !

  by the way, I am using mac-osx

  Thanks.

• Android : AMR-NB support in javacv -> ffmpeg

  1er décembre 2013, par cyberpawn

  I am trying to use AMR_NB Codec in JavaCV Android but having problems :

  This is the code i run :

  avcodec.avcodec_register_all();
  
  avformat.av_register_all();
  
  AVCodec mCodec = avcodec.avcodec_find_encoder(avcodec.AV_CODEC_ID_AMR_NB);

  Output : The mCodec is null but if I pass avcodec.AV_CODEC_ID_AAC than mCodec is not null

  I am assuming that I have to recompile ffmpeg with —enable-libopencore-amrnb. So, I downloaded Android NDKr9+ffmpeg-2.0.2+last_stable_x264 and added them to javacv-cppjars folder, I have also installed opencore-amr library in /usr/local. In ffmpeg-2.0.2-android-arm.patch i added the —enable-libopencore-amrnb flag and run following command in terminal

  ANDROID_NDK=/Users/android-ndk-r9b/ FFMPEG_VERSION=2.0.2 ./build_ffmpeg-android-arm.sh

  The script runs but the libs are not generated and the jar is empty but if I remove the —enable-libopencore-amrnb flag back then the libs are generated successfully, Please advise what am I doing wrong ? What should I do ? Any help would be greatly appreciated !

  by the way, I am using mac-osx

  Thanks.