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Make video_buffer more generic

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The video buffer took ownership of the producer frame (so that it could
swap frames quickly).

In order to support multiple sinks plugged to the decoder, the decoded
frame must not be consumed by the display video buffer.

Therefore, move the producer and consumer frames out of the video
buffer, and use FFmpeg AVFrame refcounting to share ownership while
avoiding copies.
This commit is contained in:
Romain Vimont
2021-04-11 15:01:05 +02:00
parent 5d9e96dc4e
commit 2ddf760c09
6 changed files with 77 additions and 60 deletions
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62
app/src/video_buffer.c
View File

@@ -8,24 +8,22 @@
bool
video_buffer_init(struct video_buffer *vb) {
vb->producer_frame = av_frame_alloc();
if (!vb->producer_frame) {
goto error_0;
}
vb->pending_frame = av_frame_alloc();
if (!vb->pending_frame) {
goto error_1;
return false;
}
vb->consumer_frame = av_frame_alloc();
if (!vb->consumer_frame) {
goto error_2;
vb->tmp_frame = av_frame_alloc();
if (!vb->tmp_frame) {
av_frame_free(&vb->pending_frame);
return false;
}
bool ok = sc_mutex_init(&vb->mutex);
if (!ok) {
goto error_3;
av_frame_free(&vb->pending_frame);
av_frame_free(&vb->tmp_frame);
return false;
}
// there is initially no frame, so consider it has already been consumed
@@ -36,23 +34,13 @@ video_buffer_init(struct video_buffer *vb) {
vb->cbs = NULL;
return true;
error_3:
av_frame_free(&vb->consumer_frame);
error_2:
av_frame_free(&vb->pending_frame);
error_1:
av_frame_free(&vb->producer_frame);
error_0:
return false;
}
void
video_buffer_destroy(struct video_buffer *vb) {
sc_mutex_destroy(&vb->mutex);
av_frame_free(&vb->consumer_frame);
av_frame_free(&vb->pending_frame);
av_frame_free(&vb->producer_frame);
av_frame_free(&vb->tmp_frame);
}
static inline void
@@ -73,14 +61,24 @@ video_buffer_set_consumer_callbacks(struct video_buffer *vb,
vb->cbs_userdata = cbs_userdata;
}
void
video_buffer_producer_offer_frame(struct video_buffer *vb) {
bool
video_buffer_push(struct video_buffer *vb, const AVFrame *frame) {
assert(vb->cbs);
sc_mutex_lock(&vb->mutex);
av_frame_unref(vb->pending_frame);
swap_frames(&vb->producer_frame, &vb->pending_frame);
// Use a temporary frame to preserve pending_frame in case of error.
// tmp_frame is an empty frame, no need to call av_frame_unref() beforehand.
int r = av_frame_ref(vb->tmp_frame, frame);
if (r) {
LOGE("Could not ref frame: %d", r);
return false;
}
// Now that av_frame_ref() succeeded, we can replace the previous
// pending_frame
swap_frames(&vb->pending_frame, &vb->tmp_frame);
av_frame_unref(vb->tmp_frame);
bool skipped = !vb->pending_frame_consumed;
vb->pending_frame_consumed = false;
@@ -93,19 +91,19 @@ video_buffer_producer_offer_frame(struct video_buffer *vb) {
} else {
vb->cbs->on_frame_available(vb, vb->cbs_userdata);
}
return true;
}
const AVFrame *
video_buffer_consumer_take_frame(struct video_buffer *vb) {
void
video_buffer_consume(struct video_buffer *vb, AVFrame *dst) {
sc_mutex_lock(&vb->mutex);
assert(!vb->pending_frame_consumed);
vb->pending_frame_consumed = true;
swap_frames(&vb->consumer_frame, &vb->pending_frame);
av_frame_unref(vb->pending_frame);
av_frame_move_ref(dst, vb->pending_frame);
// av_frame_move_ref() resets its source frame, so no need to call
// av_frame_unref()
sc_mutex_unlock(&vb->mutex);
// consumer_frame is only written from this thread, no need to lock
return vb->consumer_frame;
}