Problems with AAC and qtdemux

[Remco Treffkorn]

On Monday, March 19, 2012, Neil Jones wrote:
> Im trying to play MP4 files with my AAC Decoder but im having problems.
> 
> the file im playing is 'cooper.mp4' from these samples
> http://www.mp3-tech.org/tests/aac_48/samples/sample6.zip
> 
> this is a 48Khz LC-AAC with SBR (ie HE-AAC), looking a this with
> qtdemux and fakesink gives:
> 
> 
>  gst-launch -vvv filesrc location=cooper.mp4 ! qtdemux ! fakesink | more
> 
> ....
> caps = audio/mpeg, mpegversion=(int)4, framed=(boolean)true,
> stream-format=(string)raw, codec_data=(buffer)139056e5a0,
> rate=(int)44100, channels=(int)2
> ....
> 
> So as qtdemux gives us raw data (not adts or adif framed) I need to
> setup my decoder on the info provided by qtdemux, unfortunatley it
> gives me the wrong sample rate 44.1 instead of 48 and I need to know
> that the profile has SBR as this effects my decoder setup.
> 
> How do other AAC decoders deal with this? Do they just parse the raw
> data, I cant easily do this as my plugin is for a hardware decoder.
> 
> Any help appreciated,
> 
> Cheers,
> 
> Neil

Here is the output from mediainfo:

[remco at localhost sample6]$ mediainfo cooper.mp4 
General
Complete name                            : cooper.mp4
Format                                   : MPEG-4
Format profile                           : Base Media / Version 2
Codec ID                                 : mp42
File size                                : 148 KiB
Duration                                 : 24s 645ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 49.1 Kbps
Performer                                : cooper
Encoded date                             : UTC 2006-02-17 19:20:11
Tagged date                              : UTC 2006-02-17 19:20:16
Writing application                      : Nero AAC Codec 4.9.9.95

Audio
ID                                       : 1
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : HE-AAC / LC
Codec ID                                 : 40
Duration                                 : 24s 645ms
Bit rate mode                            : Variable
Bit rate                                 : 48.0 Kbps
Maximum bit rate                         : 51.2 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 44.1 KHz / 22.05 KHz
Compression mode                         : Lossy
Stream size                              : 144 KiB (97%)
Language                                 : English
Encoded date                             : UTC 2006-02-17 19:20:11
Tagged date                              : UTC 2006-02-17 19:20:16
Material_Duration                        : 24648
Material_Duration_LastFrame              : -11
Material_StreamSize                      : 146949


Please note that the bit rate is 48kb but the sampling rate is 44.1 KHz.

Cheers,
Remco

-- 
Remco Treffkorn (RT445)
HAM DC2XT
remco at rvt.com   (831) 685-1201