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avcodec/v4l2_context: Log warning when all capture buffers are in userspace 

v4l2_m2m uses device memory mapped buffers to store dequeued
frames/packets (reference counted by AVBufferRef). When the reference
count drops to zero, the buffer ownership is returned back to the
device, so that they can re-filled with frames/packets.

There are some cases when all the capture buffers are in userspace
(i.e. due to internal buffering in ffmpeg). On the s5p-mfc this causes
an infinite wait when polling to dequeue the buffers, which can be
prevented by increasing the total number of buffers. This commit adds a
warning when all the capture buffers are dequeued.

Reviewed-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Andriy Gelman <andriy.gelman@gmail.com>
This commit is contained in:
Andriy Gelman 2020-04-30 10:58:37 -04:00
parent c810a9502c
commit 2a9d623561
1 changed files with 12 additions and 0 deletions
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12
libavcodec/v4l2_context.c
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@ -291,6 +291,18 @@ static V4L2Buffer* v4l2_dequeue_v4l2buf(V4L2Context *ctx, int timeout)
};
int i, ret;
if (!V4L2_TYPE_IS_OUTPUT(ctx->type) && ctx->buffers) {
for (i = 0; i < ctx->num_buffers; i++) {
if (ctx->buffers[i].status == V4L2BUF_IN_DRIVER)
break;
}
if (i == ctx->num_buffers)
av_log(logger(ctx), AV_LOG_WARNING, "All capture buffers returned to "
"userspace. Increase num_capture_buffers "
"to prevent device deadlock or dropped "
"packets/frames.\n");
}
/* if we are draining and there are no more capture buffers queued in the driver we are done */
if (!V4L2_TYPE_IS_OUTPUT(ctx->type) && ctx_to_m2mctx(ctx)->draining) {
for (i = 0; i < ctx->num_buffers; i++) {