[FFmpeg-devel] [PATCH] avformat/fifo: add timeshift option to delay output
Marton Balint
cus at passwd.hu
Tue May 26 23:35:40 EEST 2020
Signed-off-by: Marton Balint <cus at passwd.hu>
---
doc/muxers.texi | 5 ++++
libavformat/fifo.c | 59 ++++++++++++++++++++++++++++++++++++++++++-
libavformat/version.h | 2 +-
3 files changed, 64 insertions(+), 2 deletions(-)
diff --git a/doc/muxers.texi b/doc/muxers.texi
index c598abbe66..d6f9de3702 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -2275,6 +2275,11 @@ certain (usually permanent) errors the recovery is not attempted even when
Specify whether to wait for the keyframe after recovering from
queue overflow or failure. This option is set to 0 (false) by default.
+ at item timeshift @var{duration}
+Buffer the specified amount of packets and delay writing the output. Note that
+ at var{queue_size} must be big enough to store the packets for timeshift. At the
+end of the input the fifo buffer is flushed at realtime speed.
+
@end table
@subsection Examples
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},
};
diff --git a/libavformat/version.h b/libavformat/version.h
index 493a0b337f..5c13cf1620 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -33,7 +33,7 @@
// Also please add any ticket numbers that you believe might be affected here
#define LIBAVFORMAT_VERSION_MAJOR 58
#define LIBAVFORMAT_VERSION_MINOR 43
-#define LIBAVFORMAT_VERSION_MICRO 100
+#define LIBAVFORMAT_VERSION_MICRO 101
#define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
LIBAVFORMAT_VERSION_MINOR, \
--
2.26.1
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