--- On Mon, 3/16/09, Robert Swain <[email protected]> wrote:


From: Robert Swain <[email protected]>
Subject: Re: [libav-user] Reading SLS-AAC file
To: "Libav* user questions and discussions" <[email protected]>
Date: Monday, March 16, 2009, 11:50 AM


On 15/3/09 19:04, debanjana kayal wrote:
> "SLSSpecificConfig() is not currently supported in FFmpeg's MP4/AAC code.
> I think it should be possible to demux the SLS data and remux it to
> something else useful... which would be MP4 or maybe Matroska.
>
> Could you explain more on this.When you say,SLSSpecificConfig() is not
> supported y FFMpeg do you mean that it is not possible to decode/encode
> or it is not possible to demux.

Please don't top-post. We prefer inline responses on this mailing list.

I mean parsing of the internals of SLSSpecificConfig() is not 
implemented. However, the fields you pointed out as being erroneous from 
AudioSpecificConfig() are indeed parsed before the main switch to parse 
other *SpecificConfig()s so we should be observing valid values for this.

Can you please provide the sample in which you are observing these 
erroneous values as I asked in the first response?
 
I am sorry for that it would be difficult to send you the sample data due to 
some legal obligation.

> What are you actually trying to achieve?"
>
> What I am interested in is to read the SLS specific data (e.g
> core_present, pcm_wordlength etc) from the file so that I can provide
> those information to my decoder which can then decode SLS-AAC codec.

I see. From what I have read, this is certainly possible in theory but 
we need a sample to debug.
 
Yes you are right,I was missing some bits in parsing the extradata.As mentioned 
earlier,I was getting 31 as the object index type,when you get object index 
type as 31,the object index type should modified with 32 + value of next 6 bits.

Have you implemented your own SLS-AAC decoder?

Regards,
Rob
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