This question is related to the post https://e2e.ti.com/support/wireless-connectivity/bluetooth/f/538/t/785629
The other post is about optimizing the usage of baseband packet from {2-DH5 + 2-DH3} to {2-DH5}.
Here I notice that TI CC2564C seems to waste Bluetooth transmission time by only sending 7 audio samples when the combination of baseband packets {2-DH5 + 2-DH3} would have enough payload left for an 8th audio frame.
As you can see in the Ellisys trace below, TI sends 7 audio frames encoded in SBC [Bitpool 51, Sampling 48kHz]:
As you can see in the BT trace, TI carries the 7 audio frames through a combination of {2-DH5 + 2-DH3} baseband packets.
- 2-DH5 is filled at its fullest: 679 Bytes
- BUT 2-DH3 is not filled to the maximum: TI only uses 143 Bytes when it can have payload of 367 Bytes. With SBC, Bitpool 51 and Sampling 48kHz the audio frame is 115 Bytes long. Thus TI could fill 2-DH3 with an extra audio frame.
Is it possible to optimize the usage of the Bluetooth Baseband packets to the fullest?
In the example above, we would like to request TI CC2564C to send 8 audio frames per L2CAP frame instead of 7. That would be a gain of 14% of Transmission time. That gain would be very valuable when our product faces difficult RF environment: high pathloss and high interference.
By the way, if we look at EDR-3Mbps, we have a similar situation:
- With 7 audio frames per L2CAP frame (per 3-DH5 baseband packet), TI CC2564C uses 822 Bytes of 3-DH5 payload. With 3-DH5 maximum of 1021 Bytes, we have space for an 8th audio frame of 115 Bytes.
Thanks in advance for your suggestions,
-JiBé.
