Subject: Re: [Bluez-devel] AVDTP socket?
From: Marcel Holtmann <marcel@holtmann.org>
To: BlueZ Mailing List <bluez-devel@lists.sourceforge.net>
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Date: Wed, 17 Nov 2004 16:52:33 +0100

Hi Brad,

> You noticed I have code to open and send a stream. When I send the 
> reference sbc streams byte-for-byte, I can hear a signal mixed with a 
> lot of noise. But then I don't know what the sbc parameters were for any 
> of the reference streams. Maybe it would just work if I knew that.
> 
> The reference decoder does not report the sbc parameters and I'm only 
> assuming that they have broken up the data and wrapped it in media 
> packet headers and sbc headers for a conservative mtu. The reference 
> encoder/decoder is undocumented and I didn't figure out how to set 
> parameters in the encoder. I don't want to spend any more time trying to 
> figure out the reference stuff.

the reference encoder/decoder has some command line options. You will
find them in "A2DP Test v10.pdf". The file format of the *.sbc is also
somewhere described. However I couldn't find it right now, but every
file contains a number of frames and all of them with a SBC header:

struct sbc_frame_header {
        uint8_t syncword:8;             /* Sync word */
        uint8_t subbands:1;             /* Subbands */
        uint8_t allocation_method:1;    /* Allocation method */
        uint8_t channel_mode:2;         /* Channel mode */
        uint8_t blocks:2;               /* Blocks */
        uint8_t sampling_frequency:2;   /* Sampling frequency */
        uint8_t bitpool:8;              /* Bitpool */
        uint8_t crc_check:8;            /* CRC check */
} __attribute__ ((packed));


Regards

Marcel


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