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bluetooth: Allow SCO socket packet size to be larger than mSBC frame

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With USB Alternate Setting 3 size of HCI payload is 72 bytes which is already
larger than mSBC frame size. Largest known size of HCI payload is with USB
Alternate Setting 5 (144 bytes), make it the default SCO socket MTU.

Reserve additional space in bluetooth encoder buffer to cover this case.

Since mSBC encoder and decoder will now work with larger packet sizes, drop
assertions about MTU larger than mSBC frame size.

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/617>
This commit is contained in:
Igor V. Kovalenko 2021-07-25 23:41:36 +03:00 • committed by PulseAudio Marge Bot
parent ade71b8ce7
commit d517a204de
3 changed files with 44 additions and 14 deletions
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29
src/modules/bluetooth/module-bluez5-device.c
View file

@ -260,25 +260,48 @@ static void connect_ports(struct userdata *u, void *new_data, pa_direction_t dir
static bool bt_prepare_encoder_buffer(struct userdata *u)
{
size_t encoded_size, reserved_size;
size_t encoded_size, reserved_size, encoded_frames;
pa_assert(u);
pa_assert(u->bt_codec);
/* If socket write MTU is less than encoded frame size, there could be
* up to one write MTU of data left in encoder buffer from previous round.
*
* Reserve space for 2 encoded frames to cover that.
* Reserve space for at least 2 encoded frames to cover that.
*
* Note for A2DP codecs it is expected that size of encoded frame is less
* than write link MTU. Therefore each encoded frame is sent out completely
* and there is no used space in encoder buffer before next encoder call.
*
* For SCO socket all writes will be of MTU size to match payload length
* of HCI packet. Depending on selected USB Alternate Setting the payload
* length of HCI packet may exceed encoded frame size. For mSBC frame size
* is 60 bytes, payload length of HCI packet in USB Alts 3 is 72 byte,
* in USB Alts 5 it is 144 bytes.
*
* Reserve space for up to 1 + MTU / (encoded frame size) encoded frames
* to cover that.
*
* Note for current linux kernel (up to 5.13.x at least) there is no way to
* reliably detect socket MTU size. For now we just set SCO socket MTU to be
* large enough to cover all known sizes (largest is USB ALts 5 with 144 bytes)
* and adjust SCO write size to be equal to last SCO read size. This makes
* write size less or equal to MTU size. Reserving the same number of encoded
* frames to cover full MTU is still enough.
* See also https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/254#note_779802
*/
if (u->bt_codec->get_encoded_block_size)
encoded_size = u->bt_codec->get_encoded_block_size(u->encoder_info, u->write_block_size);
else
encoded_size = u->write_block_size;
reserved_size = 2 * encoded_size;
encoded_frames = u->write_link_mtu / u->write_block_size + 1;
if (encoded_frames < 2)
encoded_frames = 2;
reserved_size = encoded_frames * encoded_size;
if (u->encoder_buffer_size < reserved_size) {
u->encoder_buffer = pa_xrealloc(u->encoder_buffer, reserved_size);