[FFmpeg-devel] [RFC][PATCH] avformat/fifo: add timeshift option to delay output
Tao Zhang
nowerzt at gmail.com
Sat May 9 05:35:58 EEST 2020
I have tested with below commands, It works fine. Thanks Marton.
ffmpeg -i input_rtmp_addr -map 0:v -map 0:a -c copy -f fifo
-timeshift 20 -queue_size 6000000 -fifo_format flv output_rtmp_addr
ffmpeg -stream_loop -1 -re -i input_file -map 0:v -map 0:a -c copy -f
fifo -timeshift 20 -queue_size 6000000 -fifo_format flv
output_rtmp_addr
Marton Balint <cus at passwd.hu> 于2020年5月8日周五 上午4:28写道：
>
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
> libavformat/fifo.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/libavformat/fifo.c b/libavformat/fifo.c
> index d11dc6626c..17748e94ce 100644
> --- a/libavformat/fifo.c
> +++ b/libavformat/fifo.c
> @@ -19,6 +19,8 @@
> * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> */
>
> +#include <stdatomic.h>
> +
> #include "libavutil/avassert.h"
> #include "libavutil/opt.h"
> #include "libavutil/time.h"
> @@ -77,6 +79,9 @@ typedef struct FifoContext {
> /* Value > 0 signals queue overflow */
> volatile uint8_t overflow_flag;
>
> + atomic_int_least64_t queue_duration;
> + int64_t last_sent_dts;
> + int64_t timeshift;
> } FifoContext;
>
> typedef struct FifoThreadContext {
> @@ -98,9 +103,12 @@ typedef struct FifoThreadContext {
> * so finalization by calling write_trailer and ff_io_close must be done
> * before exiting / reinitialization of underlying muxer */
> uint8_t header_written;
> +
> + int64_t last_received_dts;
> } FifoThreadContext;
>
> typedef enum FifoMessageType {
> + FIFO_NOOP,
> FIFO_WRITE_HEADER,
> FIFO_WRITE_PACKET,
> FIFO_FLUSH_OUTPUT
> @@ -159,6 +167,15 @@ static int fifo_thread_flush_output(FifoThreadContext *ctx)
> return av_write_frame(avf2, NULL);
> }
>
> +static int64_t next_duration(AVFormatContext *avf, AVPacket *pkt, int64_t *last_dts)
> +{
> + AVStream *st = avf->streams[pkt->stream_index];
> + int64_t dts = av_rescale_q(pkt->dts, st->time_base, AV_TIME_BASE_Q);
> + int64_t duration = (*last_dts == AV_NOPTS_VALUE ? 0 : dts - *last_dts);
> + *last_dts = dts;
> + return duration;
> +}
> +
> static int fifo_thread_write_packet(FifoThreadContext *ctx, AVPacket *pkt)
> {
> AVFormatContext *avf = ctx->avf;
> @@ -167,6 +184,9 @@ static int fifo_thread_write_packet(FifoThreadContext *ctx, AVPacket *pkt)
> AVRational src_tb, dst_tb;
> int ret, s_idx;
>
> + if (fifo->timeshift && pkt->dts != AV_NOPTS_VALUE)
> + atomic_fetch_sub_explicit(&fifo->queue_duration, next_duration(avf, pkt, &ctx->last_received_dts), memory_order_relaxed);
> +
> if (ctx->drop_until_keyframe) {
> if (pkt->flags & AV_PKT_FLAG_KEY) {
> ctx->drop_until_keyframe = 0;
> @@ -209,6 +229,9 @@ static int fifo_thread_dispatch_message(FifoThreadContext *ctx, FifoMessage *msg
> {
> int ret = AVERROR(EINVAL);
>
> + if (msg->type == FIFO_NOOP)
> + return 0;
> +
> if (!ctx->header_written) {
> ret = fifo_thread_write_header(ctx);
> if (ret < 0)
> @@ -390,12 +413,13 @@ static void *fifo_consumer_thread(void *data)
> AVFormatContext *avf = data;
> FifoContext *fifo = avf->priv_data;
> AVThreadMessageQueue *queue = fifo->queue;
> - FifoMessage msg = {FIFO_WRITE_HEADER, {0}};
> + FifoMessage msg = {fifo->timeshift ? FIFO_NOOP : FIFO_WRITE_HEADER, {0}};
> int ret;
>
> FifoThreadContext fifo_thread_ctx;
> memset(&fifo_thread_ctx, 0, sizeof(FifoThreadContext));
> fifo_thread_ctx.avf = avf;
> + fifo_thread_ctx.last_received_dts = AV_NOPTS_VALUE;
>
> while (1) {
> uint8_t just_flushed = 0;
> @@ -429,6 +453,10 @@ static void *fifo_consumer_thread(void *data)
> if (just_flushed)
> av_log(avf, AV_LOG_INFO, "FIFO queue flushed\n");
>
> + if (fifo->timeshift)
> + while (atomic_load_explicit(&fifo->queue_duration, memory_order_relaxed) < fifo->timeshift)
> + av_usleep(10000);
> +
> ret = av_thread_message_queue_recv(queue, &msg, 0);
> if (ret < 0) {
> av_thread_message_queue_set_err_send(queue, ret);
> @@ -488,6 +516,8 @@ static int fifo_init(AVFormatContext *avf)
> " only when drop_pkts_on_overflow is also turned on\n");
> return AVERROR(EINVAL);
> }
> + atomic_init(&fifo->queue_duration, 0);
> + fifo->last_sent_dts = AV_NOPTS_VALUE;
>
> oformat = av_guess_format(fifo->format, avf->url, NULL);
> if (!oformat) {
> @@ -563,6 +593,9 @@ static int fifo_write_packet(AVFormatContext *avf, AVPacket *pkt)
> goto fail;
> }
>
> + if (fifo->timeshift && pkt->dts != AV_NOPTS_VALUE)
> + atomic_fetch_add_explicit(&fifo->queue_duration, next_duration(avf, pkt, &fifo->last_sent_dts), memory_order_relaxed);
> +
> return ret;
> fail:
> if (pkt)
> @@ -576,6 +609,27 @@ static int fifo_write_trailer(AVFormatContext *avf)
> int ret;
>
> av_thread_message_queue_set_err_recv(fifo->queue, AVERROR_EOF);
> + if (fifo->timeshift) {
> + int64_t now = av_gettime_relative();
> + int64_t elapsed = 0;
> + FifoMessage msg = {FIFO_NOOP};
> + do {
> + int64_t delay = av_gettime_relative() - now;
> + if (delay < 0) { // Discontinuity?
> + delay = 10000;
> + now = av_gettime_relative();
> + } else {
> + now += delay;
> + }
> + atomic_fetch_add_explicit(&fifo->queue_duration, delay, memory_order_relaxed);
> + elapsed += delay;
> + if (elapsed > fifo->timeshift)
> + break;
> + av_usleep(10000);
> + ret = av_thread_message_queue_send(fifo->queue, &msg, AV_THREAD_MESSAGE_NONBLOCK);
> + } while (ret >= 0 || ret == AVERROR(EAGAIN));
> + atomic_store(&fifo->queue_duration, INT64_MAX);
> + }
>
> ret = pthread_join(fifo->writer_thread, NULL);
> if (ret < 0) {
> @@ -630,6 +684,9 @@ static const AVOption options[] = {
> {"recover_any_error", "Attempt recovery regardless of type of the error", OFFSET(recover_any_error),
> AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
>
> + {"timeshift", "Delay fifo output", OFFSET(timeshift),
> + AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, AV_OPT_FLAG_ENCODING_PARAM},
> +
> {NULL},
> };
>
> --
> 2.16.4
>
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