@samitouri / QOSamiQemu / commits / 27b3708292

audio/virtio-snd: fix latency calc

Media players needs meaningful latency_bytes update but it is zero now most of the time. This adds stream-wise latency_bytes calculation so that to improve the situation. Signed-off-by: Yanfeng Liu <p-liuyanfeng9@xiaomi.com> Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Message-Id: <tencent_66E8C146EA79CD00E966DEDAEF8CACD97D05@qq.com>

Yanfeng Liu committed Nov 14, 2025 at 17:34 UTC 27b370829294dcc4d1e9052e42bcd2b7cdd5c072

2 files changed +12 -1

hw/audio/virtio-snd.c

+11 -1

@@ -431,6 +431,7 @@ static uint32_t virtio_snd_pcm_prepare(VirtIOSound *s, uint32_t stream_id)

431 stream->id = stream_id;

432 stream->pcm = s->pcm;

433 stream->s = s;

434 + stream->latency_bytes = 0;

435 qemu_mutex_init(&stream->queue_mutex);

436 QSIMPLEQ_INIT(&stream->queue);

437

@@ -899,6 +900,7 @@ static void virtio_snd_handle_tx_xfer(VirtIODevice *vdev, VirtQueue *vq)

900 buffer->vq = vq;

901 buffer->size = size;

902 buffer->offset = 0;

903 + stream->latency_bytes += size;

904

905 QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);

906 }

@@ -1112,12 +1114,19 @@ error_cleanup:

1114 virtio_snd_unrealize(dev);

1115 }

1116

1117 +static inline void update_latency(VirtIOSoundPCMStream *s, size_t used)

1118 +{

1119 + s->latency_bytes = s->latency_bytes > used ?

1120 + s->latency_bytes - used : 0;

1121 +}

1122 +

1123 static inline void return_tx_buffer(VirtIOSoundPCMStream *stream,

1124 VirtIOSoundPCMBuffer *buffer)

1125 {

1126 virtio_snd_pcm_status resp = { 0 };

1127 resp.status = cpu_to_le32(VIRTIO_SND_S_OK);

1120 - resp.latency_bytes = cpu_to_le32((uint32_t)buffer->size);

1128 + update_latency(stream, buffer->size);

1129 + resp.latency_bytes = cpu_to_le32(stream->latency_bytes);

1130 iov_from_buf(buffer->elem->in_sg,

1131 buffer->elem->in_num,

1132 0,

@@ -1178,6 +1187,7 @@ static void virtio_snd_pcm_out_cb(void *data, int available)

1187 buffer->size -= size;

1188 buffer->offset += size;

1189 available -= size;

1190 + update_latency(stream, size);

1191 if (buffer->size < 1) {

1192 return_tx_buffer(stream, buffer);

1193 break;

include/hw/audio/virtio-snd.h

@@ -150,6 +150,7 @@ struct VirtIOSoundPCMStream {

150 } voice;

151 QemuMutex queue_mutex;

152 bool active;

153 + uint32_t latency_bytes;

154 QSIMPLEQ_HEAD(, VirtIOSoundPCMBuffer) queue;

155 };

156