correct way to decode AAC?
Adams, Bruce (KMLWG)
Bruce.Adams at KantarMedia.com
Tue May 22 16:41:42 UTC 2018
It looks like the avdec_aac_latm element was what I was looking for:
>$ gst-inspect-1.0 | grep aac
On a related note is it possible to construct a single pipeline that supports both decodings
as in:
aac -> avdec_aac_latm --> wavenc
-> faad -^
Is there an selectable/'or' element? as in the brackets below:
gst-launch-1.0 wavenc name=y ! filesink location=file.wav \
filesrc location=out.aac name x. ! aacparse ! (faad | avdec_aac_latm) !
audioconvert ! .y
or Something like:
gst-launch-1.0 wavenc name=y ! filesink location=file.wav \
filesrc location=out.aac name x. ! aacparse ! avdec_aac_latm !
audioconvert ! .y
which doesn't work - doubled to:
gst-launch-1.0 wavenc name=y ! filesink location=file.wav \
filesrc location=out.aac name \
x. ! aacparse ! avdec_aac_latm ! audioconvert ! .y
x. ! aacparse ! faad ! audioconvert ! .y
I do have access to information that identifies the stream type (its in the program mapping table in a DVB MPEG-TS) but I'm curious to know whether a generic pipeline is possible in principle either from the command line or from code.
Would it be a desirable patch to create an element combining both somehow (maybe a bin)?
Or is it better to be creating the pipeline dynamically once the type has been identified which I think is the only solution without changing gstreamer.
Regards,
Bruce.
-----Original Message-----
From: Adams, Bruce (KMLWG)
Sent: 22 May 2018 14:16
To: gstreamer-devel at lists.freedesktop.org
Subject: RE: correct way to decode AAC?
Hi,
That’s the same pipeline I'm using except you've added a queue.
I tried it anyway in case queue are 'more magical than I think' but perhaps unsurprisingly
it doesn't work for me.
Could it be something to do with the format. Mediainfo claims the general format is:
General
Complete name : cbbc.aac
Format : LATM
File size : 2.38 MiB
Overall bit rate mode : Variable
Audio
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Bit rate mode : Variable
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 spf)
Compression mode : Lossy
What format did you test?
Regards,
Bruce.
-----Original Message-----
From: gstreamer-devel [mailto:gstreamer-devel-bounces at lists.freedesktop.org] On Behalf Of new baby
Sent: 22 May 2018 06:20
To: gstreamer-devel at lists.freedesktop.org
Subject: Re: correct way to decode AAC?
Hi bruce,,
for audio decoding to wav format.
Hope this example works for you(i have tested it )
gst-launch-1.0 filesrc location=out.aac ! queue ! aacparse ! faad !
audioconvert ! wavenc ! filesink location=file.wav
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