[FFmpeg-trac] #3842(avformat:new): AAC (mp4a) DASH takes abnormally long to detect (~4 - 6s)

[FFmpeg]

#3842: AAC (mp4a) DASH takes abnormally long to detect (~4 - 6s)
-------------------------------------+-------------------------------------
             Reporter:  viperfx      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avformat     |                  Version:  2.2.4
             Keywords:  DASH, mp4a,  |               Blocked By:
  aac                                |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 It takes roughly ~4s for FFmpeg to detect the codec of a mp4a audio stream
 in the DASH container for an audio of length ~3m. The audio stream is from
 youtube. I have checked the location of the moov atom and it appears to be
 at the front of the file. I have spoken with devs on #ffmpeg-devel and
 they have confirmed the same issue and suggest that it should not take
 this long.

 Here is the output using boxdumper: http://tny.cz/571eb4af

 How to reproduce:
 {{{
 Obtain the youtube audio stream link using youtube-dl
 (https://github.com/rg3/youtube-dl)
 % youtube-dl -f 140 -g YOUTUBE_URL
 where YOUTUBE_URL is the url of any youtube video. Pick a music video of
 length 3-4mins so you can notice the ~4s delay.
 The youtube-dl command will print out a long URL string that you can input
 to FFmpeg or ffplay to notice the issue
 % ffmpeg -i "STREAM_URL"
 or
 % ffplay "STREAM_URL"

 My FFmpeg info:
 ffmpeg version 2.2.1 Copyright (c) 2000-2014 the FFmpeg developers
   built on Aug  9 2014 10:03:55 with Apple LLVM version 5.1
 (clang-503.0.40) (based on LLVM 3.4svn)
   configuration: --prefix=/usr/local/Cellar/ffmpeg/2.2.1 --enable-shared
 --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree
 --enable-hardcoded-tables --enable-avresample --enable-vda --cc=clang
 --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-
 libmp3lame --enable-libxvid --enable-ffplay --enable-libfdk-aac --enable-
 openssl
   libavutil      52. 66.100 / 52. 66.100
   libavcodec     55. 52.102 / 55. 52.102
   libavformat    55. 33.100 / 55. 33.100
   libavdevice    55. 10.100 / 55. 10.100
   libavfilter     4.  2.100 /  4.  2.100
   libavresample   1.  2.  0 /  1.  2.  0
   libswscale      2.  5.102 /  2.  5.102
   libswresample   0. 18.100 /  0. 18.100
   libpostproc    52.  3.100 / 52.  3.100

 Output of a typical audio stream:
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'STREAM_URL':
   Metadata:
     major_brand     : dash
     minor_version   : 0
     compatible_brands: iso6mp41
     creation_time   : 2014-03-08 01:30:29
   Duration: 00:04:00.70, start: 0.000000, bitrate: 127 kb/s
     Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo,
 fltp, 125 kb/s (default)
     Metadata:
       creation_time   : 2014-03-08 01:30:29
       handler_name    : SoundHandler
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/3842>
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