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• lavf : Add an MPEG-DASH ISOFF segmenting muxer

  6 octobre 2014, par Martin Storsjö

  lavf : Add an MPEG-DASH ISOFF segmenting muxer
  This is mostly to serve as a reference example on how to segment
  
  the output from the mp4 muxer, capable of writing the segment
  
  list in four different ways :
  
   SegmentTemplate with SegmentTimeline
  
   SegmentTemplate with implicit segments
  
   SegmentList with individual files
  
   SegmentList with one single file per track, and byte ranges
  The muxer is able to serve live content (with optional windowing)
  
  or create a static segmented MPD.
  In advanced cases, users will probably want to do the segmenting
  
  in their own application code.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] Changelog
  • [DBH] configure
  • [DBH] libavformat/Makefile
  • [DBH] libavformat/allformats.c
  • [DBH] libavformat/dashenc.c
  • [DBH] libavformat/version.h

• Reading JPEG in ffmpeg

  16 juillet 2021, par Paul Lammertsma

  I'm trying to get ffmpeg to encode several individual JPEG images into a video on Android. I've successfully built it for Android (see the configuration string at the end of this post).

  



  I can encode an h.263+ video with randomly generated frame content, and ffmpeg otherwise appears to work well.

  



  A similar question suggests that the following code should be sufficient to load an image into an AvFrame :

  



  // Make sure we have the codecs
av_register_all();

AVFormatContext *pFormatCtx;
int ret = av_open_input_file(&pFormatCtx, imageFileName, NULL, 0, NULL);

if (ret != 0) {
    printf("Can't open image file '%s': code %d, %s",
        imageFileName, ret, strerror(AVERROR(ret)));
}


  



  The above returns the correct absolute file path and error :

  



  


  Failed '/sdcard/DCIM/Camera/IMG083.jpg' : code -1094995529, Unknown error : 1094995529

  


  



  Incidentally, if I omit av_register_all(), it returns with error 2.

  



  I've compiled ffmpeg with the following arguments :

  



  


  


  ./configure —target-os=linux 
 —prefix=$PREFIX 
 —enable-cross-compile 
 —extra-libs="-lgcc" 
 —arch=arm 
 —cc=$PREBUILT/bin/arm-linux-androideabi-gcc 
 —cross-prefix=$PREBUILT/bin/arm-linux-androideabi- 
 —nm=$PREBUILT/bin/arm-linux-androideabi-nm 
 —sysroot=$PLATFORM 
 —extra-cflags=" -O3 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 -Dipv6mr_interface=ipv6mr_ifindex -fasm -Wno-psabi -fno-short-enums -fno-strict-aliasing -finline-limit=300 $OPTIMIZE_CFLAGS " 
 —enable-shared 
 —enable-static 
 —extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib -lc -lm -ldl -llog" 
 —disable-everything 
 —enable-demuxer=mov 
 —enable-demuxer=h264 
 —disable-ffplay 
 —enable-protocol=file 
 —enable-avformat 
 —enable-avcodec 
 —enable-decoder=mjpeg 
 —enable-decoder=png 
 —enable-parser=h264 
 —enable-encoder=h263 
 —enable-encoder=h263p 
 —disable-network 
 —enable-zlib 
 —disable-avfilter 
 —disable-avdevice

  


  


  



  Any suggestions would be most welcome !

  


• MPEG-2 AAC frame-by-frame audio decoding

  3 mai 2018, par Jonathan May

  I have individual audio frames encoded in MPEG-2 AAC. Each frame consists of 1024 16 bit PCM samples.

  I notice that each AAC frame is a different size. I assume this is a result of the MPEG-2 AAC compression algorithm and perfectly normal.

  I need a way to decode a single frame and get back the original 1024 PCM samples (with error from lossy compression, that’s fine).

  I couldn’t find information about the MPEG-2 AAC algorithm ANYWHERE online. It’s kinda nuts.

  I’ve been trying a crude work around using a library called pydub, which contains a few methods which use FFMPEG’s AAC decoder. Trying to load the audio frame as an AudioSegment using AAC encoding :

  audioData = BytesIO(frame)
  
  sound = AudioSegment.from_file(audioData, format="aac")

  gives the following error :

  [aac @ 000002d444c1aa00] Estimating duration from bitrate, this may be inaccurate\r\n
  
  Input #0, aac, from 'C:\\Users\\jmk_m\\AppData\\Local\\Temp\\tmpjl3x0xao':\r\n
  
    Duration: 00:00:00.19, bitrate: 23 kb/s\r\n
  
  Stream #0:0: Audio: aac (LC), 22050 Hz, mono, fltp, 23 kb/s\r\nStream mapping:\r\n
  
  Stream #0:0 -> #0:0 (aac (native) -> pcm_s16le (native))\r\n
  
  Press [q] to stop, [?] for help\r\n
  
  Output #0, wav, to 'C:\\Users\\jmk_m\\AppData\\Local\\Temp\\tmpxmp942e4':\r\n
  
  Metadata:\r\n
  
  ISFT            : Lavf58.10.100\r\n
  
  Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 22050 Hz, mono, s16, 352 kb/s\r\n
  
  Metadata:\r\n      encoder         : Lavc58.13.100 pcm_s16le\r\n
  
  [aac @ 000002d444cc7480] Reserved bit set.\r\n
  
  [aac @ 000002d444cc7480] Prediction is not allowed in AAC-LC.\r\n
  
  Error while decoding stream #0:0: Invalid data found when processing input\r\n
  
  [aac @ 000002d444cc7480] Reserved bit set.\r\n
  
  [aac @ 000002d444cc7480] Prediction is not allowed in AAC-LC.\r\n
  
  Error while decoding stream #0:0: Invalid data found when processing input\r\n
  
  [aac @ 000002d444cc7480] Prediction is not allowed in AAC-LC.\r\n
  
  Error while decoding stream #0:0: Invalid data found when processing input\r\n
  
  size=       2kB time=00:00:00.04 bitrate= 366.2kbits/s speed=5.45x    \r\n
  
  video:0kB audio:2kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 3.808594%\r\n
  
  Conversion failed!\r\n"

  If anyone has any insights as to what may be causing the error, or any alternative approaches, that’d be greatly appreciated !