[FFmpeg-devel] [PATCH] avformat/fifo: add timeshift option to delay output

Marton Balint cus at passwd.hu
Mon Jun 8 03:01:18 EEST 2020



On Tue, 26 May 2020, Marton Balint wrote:

> 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(-)

Ping, will apply soon.

Thanks,
Marton

>
> 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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