Advait,
Let me work on explaining the details, since I am working on this feature. The issue that we see seems to be the same as the noted thread. In the case where the device is the initiator, the Watch demo does not seem to be quite correct.
The first issue is that the advertised capabilities of the Source device (Watch demo) does not match the A2DP specification. For example:
/* SBC codec capabilities */
static const wiced_bt_a2d_sbc_cie_t av_sbc_caps =
{
/* samp_freq */ (A2D_SBC_IE_SAMP_FREQ_16|A2D_SBC_IE_SAMP_FREQ_32|A2D_SBC_IE_SAMP_FREQ_44|A2D_SBC_IE_SAMP_FREQ_48),
/* ch_mode */
(A2D_SBC_IE_CH_MD_MONO | A2D_SBC_IE_CH_MD_JOINT), // A2D_SBC_IE_CH_MD_DUAL | A2D_SBC_IE_CH_MD_STEREO
/* block_len */
(A2D_SBC_IE_BLOCKS_16), //A2D_SBC_IE_BLOCKS_8|A2D_SBC_IE_BLOCKS_12|A2D_SBC_IE_BLOCKS_16|
/* num_subbands */
(A2D_SBC_IE_SUBBAND_8), //A2D_SBC_IE_SUBBAND_4|A2D_SBC_IE_SUBBAND_8
/* alloc_mthd */
(A2D_SBC_IE_ALLOC_MD_S), //A2D_SBC_IE_ALLOC_MD_S|A2D_SBC_IE_ALLOC_MD_L
/* max_bitpool */
(AV_SBC_MAX_BITPOOL), //A2D_SBC_IE_MAX_BITPOOL
/* min_bitpool */
(A2D_SBC_IE_MIN_BITPOOL) //A2D_SBC_IE_MIN_BITPOOL
};
Let's just take one field the alloc_mthd. We are specifying that we only support the SNR method, but the A2DP standard says that we MUST support Loudness method. When we send this to some devices, the responding configuration data is malformed with the alloc method set to 0x00 which is not valid. The block length also does not indicate that we support all block lengths as required by the A2DP specification.
The other issue that is seen is that the code and thus my derived code is very sensitive to timing differences of the messages coming from the peer device in initiator mode. There are a few notes to this issue in the sample code, but no actual code to address those cases.
In the case of Airpods, we can connect, pair and open a connection, but have not been able to get audio using the SBC codec. This happens on our internal firwmware, and the Watch Demo. Using the Watch demo with the control program, I can play tones on all other devices, but no sound with come out of the Airpods with the same setup at the other peer devices (speakers, headphones)
