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• How to seek mp4 aac audio using Media Source Extensions

  29 août 2018, par Chris

  Please can someone offer me a few pointers when trying to seek within streamed aac audio in mp4 containers ? I’m trying to develop a music download service that sips data via ranged requests rather than simply link to a mp4 file as an <audio></audio> src. (which will instead buffer the whole file as quickly as possible, and so be rather wasteful and expensive).

  So far I’ve managed to successfully append sequential audio range buffers to the SourceBuffer object using partial/ranged requests, attached to my suitably mime-typed MediaSource object. But as soon as I try to seek, the wheels come off and I receive a ’CHUNK_DEMUXER_ERROR_APPEND_FAILED’ error, with the specific issue : ’stream parsing failed’.

  I’ve prepared my mp4 files by encoding them with ffmpeg (via the fluent ffmpeg module), rewriting the movie header box at the start of the file (via the -movflags faststart setting) so that the duration can be parsed. I then fragment the file with mp4fragment (part of the Bento4 tools) with the default settings, and check to ensure the structure of the file matches the format specified by ISO BMFF, with pairs of movie fragments and data boxes (moof/mdat) describing the audio stream. Given the source buffer has no problem playing from the beginning, with contiguous subsequent ranges, this appears to confirm that the format of the mp4 file is acceptable.

  As an aside, I’ve tried fragmenting the file completely in ffmpeg/fluent ffmpeg (using the ’-movflags empty_moov+default_base_moof’ options), but while this works, it also removes the duration from the moov as you’d expect, so the file gets larger during playback as more fragments are fetched and appended. If I set the file duration manually, I still have the issue of not being able to seek to unbuffered audio, so I only seem to be making life more difficult trying to fragment the file solely in ffmpeg.

  So how should I go about seeking within the stream ? I gather that seeking effectively ’needle-drops’ randomly, and so the source buffer might struggle to parse the data out of context, but I imagined that it would skip to the next available fragment in the range that I fetch (which is calculated using the percentage of the seek bar width to set the player.currentTime, which is then converted to a suitable byte range using the 128kbps CBR figure to convert seconds to bytes, to send a 206 partial range request).

  I’ve seen mention of buffer offsets, but I don’t understand how these apply. Most of the dev examples I’ve seen just focus on whole files or segmented videos, rather than fragmented single audio files for seeking ? Do I need to somehow retain a portion of the data from the moov box when seeking for the source buffer to be able to parse it ? In the trun box I have a data offset that varies between two values throughout the file, 444 and 448, depending on whether the sample count is 86 or 87. I’m not sure why it’s not consistent.

  Here’s what the moov looks like from my audio file :

  [ftyp] size=8+24
  
    major_brand = isom
  
    minor_version = 200
  
    compatible_brand = isom
  
    compatible_brand = iso2
  
    compatible_brand = mp41
  
    compatible_brand = iso5
  
  [moov] size=8+620
  
    [mvhd] size=12+96
  
      timescale = 1000
  
      duration = 350047
  
      duration(ms) = 350047
  
    [trak] size=8+448
  
      [tkhd] size=12+80, flags=7
  
        enabled = 1
  
        id = 1
  
        duration = 350047
  
        width = 0.000000
  
        height = 0.000000
  
      [edts] size=8+28
  
        [elst] size=12+16
  
          entry count = 1
  
          entry/segment duration = 350000
  
          entry/media time = 2048
  
          entry/media rate = 1
  
      [mdia] size=8+312
  
        [mdhd] size=12+20
  
          timescale = 44100
  
          duration = 0
  
          duration(ms) = 0
  
          language = und
  
        [hdlr] size=12+41
  
          handler_type = soun
  
          handler_name = Bento4 Sound Handler
  
        [minf] size=8+219
  
          [smhd] size=12+4
  
            balance = 0
  
          [dinf] size=8+28
  
            [dref] size=12+16
  
              [url ] size=12+0, flags=1
  
                location = [local to file]
  
          [stbl] size=8+159
  
            [stsd] size=12+79
  
              entry-count = 1
  
              [mp4a] size=8+67
  
                data_reference_index = 1
  
                channel_count = 2
  
                sample_size = 16
  
                sample_rate = 44100
  
                [esds] size=12+27
  
                  [ESDescriptor] size=2+25
  
                    es_id = 0
  
                    stream_priority = 0
  
                    [DecoderConfig] size=2+17
  
                      stream_type = 5
  
                      object_type = 64
  
                      up_stream = 0
  
                      buffer_size = 0
  
                      max_bitrate = 128006
  
                      avg_bitrate = 128006
  
                      DecoderSpecificInfo = 12 10 
  
                    [Descriptor:06] size=2+1
  
            [stts] size=12+4
  
              entry_count = 0
  
            [stsc] size=12+4
  
              entry_count = 0
  
            [stsz] size=12+8
  
              sample_size = 0
  
              sample_count = 0
  
            [stco] size=12+4
  
              entry_count = 0
  
    [mvex] size=8+48
  
      [mehd] size=12+4
  
        duration = 350047
  
      [trex] size=12+20
  
        track id = 1
  
        default sample description index = 1
  
        default sample duration = 0
  
        default sample size = 0
  
        default sample flags = 0

  And here’s a typical fragment :

  [moof] size=8+428
  
    [mfhd] size=12+4
  
      sequence number = 1
  
    [traf] size=8+404
  
      [tfhd] size=12+8, flags=20008
  
        track ID = 1
  
        default sample duration = 1024
  
      [tfdt] size=12+8, version=1
  
        base media decode time = 0
  
      [trun] size=12+352, flags=201
  
        sample count = 86
  
        data offset = 444
  
  [mdat] size=8+32653

  Does that all look good ? Any pointers for seeking within such a file would be hugely appreciated. Thanks !

• Android Media player/framework species

  4 septembre 2018, par sungyong

  I’m confused about species of media player/framework/library of Android and it’s role and positions.

  Here is my understanding about Android media player and framework.
  

  I don’t have confident what I understand, still be under the chaos.

  From Android developer’s guide,
  for application side : apk uses Application Framework which has two players - MediaPlayer, ExoPlayer

  for Native framework side : it has also various players - Nu, awesome, etc.

  There’re some query for gstreamer vs ffmpeg, ffmpeg vs vlc, or exoplayer vs vitamio. It makes me more confusing.

  Would you clearify me to get the right concept for them ?
  If my android custom device use ffmpeg, that means it doesn’t use standard Android media framework ?

  For stagefright engine, there is no alternative for this ?

• Unable to decode media issue on chrome browser

  20 octobre 2018, par Shrikant D

  I am experiencing an issue while playing media on my application. I am using html5 player which works fine on another browser but the media not worked on Google Chrome. Below is the ffmpeg output.

  ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
  
  
  
    built with Apple LLVM version 8.0.0 (clang-800.0.42.1)
  
  
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/3.4.1 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-libmp3lame --enable-libx264 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma
  
  
  
    libavutil      55. 78.100 / 55. 78.100
  
  
  
    libavcodec     57.107.100 / 57.107.100
  
  
  
    libavformat    57. 83.100 / 57. 83.100
  
  
  
    libavdevice    57. 10.100 / 57. 10.100
  
  
  
    libavfilter     6.107.100 /  6.107.100
  
  
  
    libavresample   3.  7.  0 /  3.  7.  0
  
  
  
    libswscale      4.  8.100 /  4.  8.100
  
  
  
    libswresample   2.  9.100 /  2.  9.100
  
  
  
    libpostproc    54.  7.100 / 54.  7.100
  
  
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'sources-5a6b388fb093f.mp4':
  
  
  
    Metadata:
  
  
  
      major_brand     : mp42
  
  
  
      minor_version   : 0
  
  
  
      compatible_brands: mp42mp41
  
  
  
      creation_time   : 2017-10-31T01:45:10.000000Z
  
  
  
    Duration: 00:04:55.72, start: 0.000000, bitrate: 10300 kb/s
  
  
  
      Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 9975 kb/s, 59.94 fps, 59.94 tbr, 60k tbn, 119.88 tbc (default)
  
  
  
      Metadata:
  
  
  
        creation_time   : 2017-10-31T01:45:10.000000Z
  
  
  
        handler_name    : Alias Data Handler
  
  
  
        encoder         : AVC Coding
  
  
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 317 kb/s (default)
  
  
  
      Metadata:
  
  
  
        creation_time   : 2017-10-31T01:45:10.000000Z
  
  
  
        handler_name    : Alias Data Handler

  The issue is replicable on Windows, Linux/Ubuntu and Mac on Google Chrome browser.

  UPDATED :

  render_id: 56
  
  player_id: 0
  
  origin_url: https://example.com/
  
  frame_url: https://example.com/node/83810
  
  frame_title: 
  
  url: https://example.com/sites/default/files/sources-5a6b388fb093f.mp4
  
  total_bytes: 380754023
  
  streaming: false
  
  single_origin: true
  
  passed_cors_access_check: false
  
  range_header_supported: true
  
  pipeline_state: kStopped
  
  info: Selected FFmpegVideoDecoder for video decoding, config: codec: h264 format: 1 profile: h264 main coded size: [1920,1080] visible rect: [0,0,1920,1080] natural size: [1920,1080] has extra data? true encryption scheme: Unencrypted rotation: 0°
  
  audio_channels_count: 2
  
  audio_codec_name: aac
  
  audio_sample_format: Float 32-bit planar
  
  audio_samples_per_second: 48000
  
  bitrate: 10300299
  
  found_audio_stream: true
  
  found_video_stream: true
  
  height: 1080
  
  max_duration: 295.722667
  
  start_time: 0
  
  time_base: 1/60000
  
  video_codec_name: h264
  
  video_format: PIXEL_FORMAT_I420
  
  video_is_encrypted: false
  
  width: 1920
  
  audio_dds: false
  
  audio_decoder: FFmpegAudioDecoder
  
  video_dds: false
  
  video_decoder: FFmpegVideoDecoder
  
  audio_buffering_state: BUFFERING_HAVE_ENOUGH
  
  video_buffering_state: BUFFERING_HAVE_ENOUGH
  
  for_suspended_start: false
  
  pipeline_buffering_state: BUFFERING_HAVE_ENOUGH
  
  duration: 295.722667
  
  event: PAUSE
  
  error: video decode error
  
  pipeline_error: PIPELINE_ERROR_DECODE

  Added chrome Player Properties for specific media.