Recherche avancée

Sur d’autres sites (7299)

• Launching ffmpeg from inside my C code doesn't convert video stream from fifo

  13 mai 2017, par abraxas1

  (Beaglebone Black, ubuntu 16.04 linux 4.4.62-ti-r99)

  I have a raw h264 feed coming into my C program (into a callback from a custom API) and then I named-piped the raw h264 to a file and this CLI command converts that file successfully.

  ffmpeg -report -re -framerate 30 -y -f h264 -i orbi_0148.cam1.h264 -c:v copy -an -video_size 1920x1080 -f mp4 orbi_0148.cam1-1.mp4

  I then try to launch this command from my program with the same options using execv(),

  first mkfifo the fifo’s,

  then launch ffmpeg (shown below) starts the streaming form the cameras to my callback function, and out to the fifos.

  I close the fifos at the end of video recording, and don’t get any file created and get this output, which I don’t understand at all.
  (the successful command line output follows below this output generated from execv())
  thanks, any help much appreciated.
  hardware has come in now and the spot light is on me.

  (execv output with options -report -y -i /tmp/fifocam3.h264 -c:v copy -an -video_size 1920x1080 -f mp4 /media/sd-card/orbi_0140.cam3.mp4)

  root@arm:/home/orbi# cat ffmpeg-20170511-001941.log 
  
  ffmpeg started on 2017-05-11 at 00:19:41
  
  Report written to "ffmpeg-20170511-001941.log"
  
  Command line:
  
  /usr/bin/ffmpeg -report -y -i /tmp/fifocam3.h264 -c:v copy -an -video_size 1920x1080 -f mp4 /media/sd-card/orbi_0140.cam3.mp4
  
  ffmpeg version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2000-2017 the FFmpeg developers
  
  
  
    built with gcc 5.4.0 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.4) 20160609
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/arm-linux-gnueabihf --incdir=/usr/include/arm-linux-gnueabihf --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11gr  libavutil      54. 31.100 / 54. 31.100
  
    libavcodec     56. 60.100 / 56. 60.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 40.101 /  5. 40.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Splitting the commandline.
  
  Reading option '-report' ... matched as option 'report' (generate a report) with argument '1'.
  
  Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
  
  Reading option '-i' ... matched as input url with argument '/tmp/fifocam3.h264'.
  
  Reading option '-c:v' ... matched as option 'c' (codec name) with argument 'copy'.
  
  Reading option '-an' ... matched as option 'an' (disable audio) with argument '1'.
  
  Reading option '-video_size' ... matched as AVOption 'video_size' with argument '1920x1080'.
  
  Reading option '-f' ... matched as option 'f' (force format) with argument 'mp4'.
  
  Reading option '/media/sd-card/orbi_0140.cam3.mp4' ... matched as output url.
  
  Finished splitting the commandline.
  
  Parsing a group of options: global .
  
  Applying option report (generate a report) with argument 1.
  
  Applying option y (overwrite output files) with argument 1.
  
  …
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input url /tmp/fifocam3.h264.
  
  …
  
  Successfully parsed a group of options.
  
  Opening an input file: /tmp/fifocam3.h264.
  
  [h264 @ 0xf249a0] Format h264 probed with size=2048 and score=51
  
  [h264 @ 0xf249a0] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0
  
  [h264 @ 0xf25460] Current profile doesn't provide more RBSP data in PPS, skipping
  
  [h264 @ 0xf25460] bytestream overread -4
  
  [h264 @ 0xf25460] bytestream overread -4
  
  [h264 @ 0xf25460] bytestream overread -4
  
  [h264 @ 0xf25460] bytestream overread -4
  
  [h264 @ 0xf25460] bytestream overread -10
  
  [h264 @ 0xf25460] error while decoding MB 112 28, bytestream -10
  
  [h264 @ 0xf25460] concealing 4737 DC, 4737 AC, 4737 MV errors in P frame
  
  [h264 @ 0xf25460] Frame num gap 7 5
  
  
  
  
  
  /////// successful command line run  \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
  
  root@arm:/home/orbi# ffmpeg -report -re -framerate 30 -y -f h264 -i orbi_0148.cam1.h264 -c:v copy -an -video_size 1920x1080 -f mp4 orbi_0148.cam1-1.mp4
  
  
  
  root@arm:/home/orbi# cat ffmpeg-20170511-002629.log 
  
  ffmpeg started on 2017-05-11 at 00:26:29
  
  Report written to "ffmpeg-20170511-002629.log"
  
  Command line:
  
  ffmpeg -report -re -framerate 30 -y -f h264 -i orbi_0148.cam1.h264 -c:v copy -an -video_size 1920x1080 -f mp4 orbi_0148.cam1-1.mp4
  
  ffmpeg version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.4) 20160609
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/arm-linux-gnueabihf --incdir=/usr/include/arm-linux-gnueabihf --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11gr  libavutil      54. 31.100 / 54. 31.100
  
    libavcodec     56. 60.100 / 56. 60.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 40.101 /  5. 40.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Splitting the commandline.
  
  Reading option '-report' ... matched as option 'report' (generate a report) with argument '1'.
  
  Reading option '-re' ... matched as option 're' (read input at native frame rate) with argument '1'.
  
  Reading option '-framerate' ... matched as AVOption 'framerate' with argument '30'.
  
  Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
  
  Reading option '-f' ... matched as option 'f' (force format) with argument 'h264'.
  
  Reading option '-i' ... matched as input url with argument 'orbi_0148.cam1.h264'.
  
  Reading option '-c:v' ... matched as option 'c' (codec name) with argument 'copy'.
  
  Reading option '-an' ... matched as option 'an' (disable audio) with argument '1'.
  
  Reading option '-video_size' ... matched as AVOption 'video_size' with argument '1920x1080'.
  
  Reading option '-f' ... matched as option 'f' (force format) with argument 'mp4'.
  
  Reading option 'orbi_0148.cam1-1.mp4' ... matched as output url.
  
  Finished splitting the commandline.
  
  Parsing a group of options: global .
  
  Applying option report (generate a report) with argument 1.
  
  Applying option y (overwrite output files) with argument 1.
  
  …
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input url orbi_0148.cam1.h264.
  
  Applying option re (read input at native frame rate) with argument 1.
  
  Applying option f (force format) with argument h264.
  
  …
  
  Successfully parsed a group of options.
  
  Opening an input file: orbi_0148.cam1.h264.
  
  [h264 @ 0x848a20] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0
  
  [h264 @ 0x8515b0] Current profile doesn't provide more RBSP data in PPS, skipping
  
  [h264 @ 0x8515b0] Current profile doesn't provide more RBSP data in PPS, skipping
  
  [h264 @ 0x848a20] max_analyze_duration 5000000 reached at 5005000 microseconds st:0
  
  [h264 @ 0x848a20] After avformat_find_stream_info() pos: 3773440 bytes read:3801088 seeks:0 frames:152
  
  Input #0, h264, from 'orbi_0148.cam1.h264':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0, 152, 1/1200000: Video: h264 (Main), yuv420p(tv), 1920x1080, 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
  
  Successfully opened the file.
  
  Parsing a group of options: output url orbi_0148.cam1-1.mp4.
  
  …
  
  Applying option c:v (codec name) with argument copy.
  
  Applying option an (disable audio) with argument 1.
  
  Applying option f (force format) with argument mp4.
  
  Successfully parsed a group of options.
  
  Opening an output file: orbi_0148.cam1-1.mp4.
  
  Successfully opened the file.
  
  [mp4 @ 0x8fb230] Codec for stream 0 does not use global headers but container format requires global headers
  
  Output #0, mp4, to 'orbi_0148.cam1-1.mp4':
  
    Metadata:
  
      encoder         : Lavf56.40.101
  
      Stream #0:0, 0, 1/1200000: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 1920x1080, q=2-31, 29.97 fps, 29.97 tbr, 1200k tbn, 1200k tbc
  
  …
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Press [q] to stop, [?] for help
  
  [NULL @ 0x8515b0] Current profile doesn't provide more RBSP data in PPS, skipping    
  
  No more output streams to write to, finishing.e=00:00:08.64 bitrate=5887.7kbits/s    
  
  frame=  270 fps= 30 q=-1.0 Lsize=    6443kB time=00:00:08.97 bitrate=5880.6kbits/s    
  
  video:6440kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.056839%
  
  Input file #0 (orbi_0148.cam1.h264):
  
    Input stream #0:0 (video): 270 packets read (6594052 bytes); 
  
    Total: 270 packets (6594052 bytes) demuxed
  
  Output file #0 (orbi_0148.cam1-1.mp4):
  
    Output stream #0:0 (video): 270 packets muxed (6594052 bytes); 
  
    Total: 270 packets (6594052 bytes) muxed
  
  0 frames successfully decoded, 0 decoding errors
  
  [AVIOContext @ 0x931650] Statistics: 34 seeks, 308 writeouts
  
  [AVIOContext @ 0x851190] Statistics: 6594052 bytes read, 0 seeks

• FFMPEG to create an MPEG-DASH stream with VP8

  24 avril 2017, par Kenneth Worden

  I’m trying to use FFMPEG to stream a live video feed from my webcam /dev/video0. Following scattered tutorials and scarce documentation (is this a known problem for the encoding community ?) I arrived at the following bash script :

  #!/bin/bash
  
  
  
  ffmpeg \
  
      -y \
  
      -f v4l2 \
  
          -i /dev/video0 \
  
          -s 640x480 \
  
          -input_format mjpeg \
  
          -r 24 \
  
      -map 0:0 \
  
      -pix_fmt yuv420p \
  
      -codec:v libvpx \
  
          -s 640x480 \
  
          -threads 4 \
  
          -b:v 50k \
  
          -tile-columns 4 \
  
          -frame-parallel 1 \
  
          -keyint_min 24 -g 24 \
  
      -f webm_chunk \
  
          -header "stream.hdr" \
  
          -chunk_start_index 1 \
  
      stream_%d.chk &
  
  
  
  sleep 2
  
  
  
  ffmpeg \
  
      -f webm_dash_manifest -live 1 \
  
      -i stream.hdr \
  
      -c copy \
  
      -map 0 \
  
      -f webm_dash_manifest -live 1 \
  
          -adaptation_sets "id=0,streams=0" \
  
          -chunk_start_index 1 \
  
          -chunk_duration_ms 1000 \
  
          -time_shift_buffer_depth 30000 \
  
          -minimum_update_period 60000 \
  
      stream_manifest.mpd

  When I run this script, my webcam light turns on, the stream.hdr and stream_manifest.mpd files are written, and chunks start to be created (i.e. stream_1.chk, stream_2.chk, etc...). However, FFMPEG throws the following error :

  Could not write header for output file #0 (incorrect codec parameters
   ?) : Invalid data found when processing input

  I will explain what I think I am doing with this script, and hopefully this will expose any errors in my thinking.

  First, we invoke FFMPEG to use Video for Linux 2 (v4l2) to read from my webcam (/dev/video0) of a resolution 640x480. The input format is mjpeg with a framerate of 24fps.

  I then declare that FFMPEG should "map" (copy) the video stream output by v4l2 to a file. I specify the pixel format (YUV420P) and use libvpx (VP8 encoding) to encode the video stream. I set the size to be 640x480, use 4 threads, set the bitrate to be 50kbps, do some magic with tile-columns and frame-parallel options, and set the I-frames to be 24 frames apart.

  I then create a stream.hdr file. The starting index is 1. This command continues to run infinitely until I kill it, grabbing new video from my webcam and outputting it into chunks.

  I then sleep for 2 seconds to give the previous command time to generate a header file.

  And that’s really it. The next invocation of FFMPEG simply creates the MPEG-DASH manifest file given the header generated in the previous step.

  So what’s going on ? Why can I not view the video in a web browser (I’m using Dash.js) ? I serve the manifest, header, and chunks on a Node.js server so that trivial issue is not the problem.

  ---

  Edit : Here is my full console output.

  ffmpeg version 3.0.7-0ubuntu0.16.10.1 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 6.2.0 (Ubuntu 6.2.0-5ubuntu12) 20161005
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.10.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librubberband --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-chromaprint --enable-libx264
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libavresample   3.  0.  0 /  3.  0.  0
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  [video4linux2,v4l2 @ 0x55847e244ea0] The driver changed the time per frame from 1/24 to 1/30
  
  [mjpeg @ 0x55847e245c00] Changing bps to 8
  
  Input #0, video4linux2,v4l2, from '/dev/video0':
  
    Duration: N/A, start: 64305.102081, bitrate: N/A
  
      Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 640x480, -5 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
  
  Codec AVOption frame-parallel (Enable frame parallel decodability features) specified for output file #0 (stream_%d.chk) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
  
  Codec AVOption tile-columns (Number of tile columns to use, log2) specified for output file #0 (stream_%d.chk) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
  
  [swscaler @ 0x55847e24b720] deprecated pixel format used, make sure you did set range correctly
  
  [libvpx @ 0x55847e248a20] v1.5.0
  
  Output #0, webm_chunk, to 'stream_%d.chk':
  
    Metadata:
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: vp8 (libvpx), yuv420p, 640x480, q=-1--1, 50 kb/s, 30 fps, 30 tbn, 30 tbc
  
      Metadata:
  
        encoder         : Lavc57.24.102 libvpx
  
      Side data:
  
        unknown side data type 10 (24 bytes)
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mjpeg (native) -> vp8 (libvpx))
  
  Press [q] to stop, [?] for help
  
  frame=   21 fps=0.0 q=0.0 size=N/A time=00:00:00.70 bitrate=N/A dup=5 drop=frame=   36 fps= 35 q=0.0 size=N/A time=00:00:01.20 bitrate=N/A dup=5 drop=frame=   51 fps= 33 q=0.0 size=N/A time=00:00:01.70 bitrate=N/A dup=5 drop=ffmpeg version 3.0.7-0ubuntu0.16.10.1 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 6.2.0 (Ubuntu 6.2.0-5ubuntu12) 20161005
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.10.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librubberband --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-chromaprint --enable-libx264
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libavresample   3.  0.  0 /  3.  0.  0
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, webm_dash_manifest, from 'stream.hdr':
  
    Metadata:
  
      encoder         : Lavf57.25.100
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: vp8, yuv420p, 640x480, SAR 1:1 DAR 4:3, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
  
      Metadata:
  
        webm_dash_manifest_file_name: stream.hdr
  
        webm_dash_manifest_track_number: 1
  
  Output #0, webm_dash_manifest, to 'stream_manifest.mpd':
  
    Metadata:
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: vp8, yuv420p, 640x480 [SAR 1:1 DAR 4:3], q=2-31, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
  
      Metadata:
  
        webm_dash_manifest_file_name: stream.hdr
  
        webm_dash_manifest_track_number: 1
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Could not write header for output file #0 (incorrect codec parameters ?): Invalid data found when processing input
  
  frame=   67 fps= 33 q=0.0 size
  
  frame=   82 fps= 32 q=0.0 size=N/A time=00:00:02.73 bitrate=N/A dup=5 drop=
  
  frame=   97 fps= 32 q=0.0 size=N/A time=00:00:03.23 bitrate=N/A dup=5 drop=
  
  frame=  112 fps= 32 q=0.0 size=N/A time=00:00:03.73 bitrate=N/A dup=5 ...

• Chrome’s New Audio Notifier

  30 janvier 2014, par Multimedia Mike — General

  Version 32 of Google’s Chrome web browser introduced this nifty feature :

  
  
  

  When a browser tab has an element that is producing audio, the browser’s tab shows the above audio notification icon to inform the user. I have seen that people have a few questions about this, specifically :

  1. How does this feature work ?
  2. Why wasn’t this done sooner ?
  3. Are other browsers going to follow suit ?

  Short answers : 1) Chrome offers a new plugin API that the Flash Player is now using, as are Chrome’s internal media playing facilities ; 2) this feature was contingent on the new plugin infrastructure mentioned in the previous answer ; 3) other browsers would require the same infrastructure support.

  Longer answers follow…

  Plugin History
  Plugins were originally based on the Netscape Plugin API. This was developed in the early 1990s in order to support embedding PDFs into the Netscape web browser. The NPAPI does things like providing graphics contexts for drawing and input processing, and mediate network requests through the browser’s network facilities.

  What NPAPI doesn’t do is handle audio. In the early-mid 1990s, audio support was not a widespread consideration in the consumer PC arena. Due to the lack of audio API support, if a plugin wanted to play audio, it had to go outside of the plugin framework.

  
  
  

  There are a few downsides to this approach :

  • If a plugin wants to play audio, it needs to access unique audio APIs on each supported platform. One of the most famous things I’ve ever written deals concerns this nightmare on Linux. (The picture worth a thousand words.)
  • Plugin necessarily needs free unrestricted access to system facilities, i.e., security measures like sandboxing become more difficult without restricting functionality.
  • Since the browser doesn’t mediate access to the audio APIs, the browser can’t reasonably be expected to know when a plugin is accessing the audio resources.

  So that last item hopefully answers the question of why it has been so difficult for NPAPI-supporting browsers to implement what seems like it would be simple functionality, like implementing a per-tab audio notifier.

  Plugin Future
  Since Google released Chrome in an effort to facilitate advancements on the client side of the internet, they have made numerous efforts to modernize various legacy aspects of web technology. These efforts include the SPDY protocol, Native Client, WebM/WebP, and something call the Pepper Plugin API (PPAPI). This is a more modern take on the classic plugin architecture to supplant the aging NPAPI :

  
  
  

  Right away, we see that the job of the plugin writer is greatly simplified. Where was this API years ago when I was writing my API jungle piece ?

  The Linux version of Chrome was apparently the first version that packaged the Pepper version of the Flash Player (doing so fixed an obnoxious bug in the Linux Flash Player interaction with GTK). Now, it looks like Windows and Mac have followed suit. Digging into the Chrome directory on a Windows 7 installation :

  AppData\Local\Google\Chrome\Application[version]\PepperFlash\pepflashplayer.dll

  This directory exists for version 31 as well, which is still hanging around my system.

  So, to re-iterate : Chrome has a new plugin API that plugins use to access the audio API. Chrome knows when the API is accessed and that allows the browser to display the audio notifier on a tab.

  Other Browsers
  What about other browsers ? “Mozilla is not interested in or working on Pepper at this time. See the Chrome Pepper pages.”