[FFmpeg-trac] #3842(avformat:new): AAC (mp4a) DASH takes abnormally long to detect (~4 - 6s)
FFmpeg
trac at avcodec.org
Sun Aug 10 12:47:44 CEST 2014
#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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