On 5/1/2019 11:13 AM, Moritz Barsnick wrote:
> Works for video and audio streams.
>
> Similar to the "-re" option in ffmpeg, but unlike that option does not
> only work for input files, and is not only implemented for the
> command line tool. This filter is available through the libraries,
> and unlike the "realtime" filter also works when using the "copy"
> encoder.
>
> Implementation mostly taken from libavfilter/f_realtime.c.
> ---
> doc/bitstream_filters.texi | 24 +++++++++++
> libavcodec/Makefile | 1 +
> libavcodec/bitstream_filters.c | 1 +
> libavcodec/realtime_bsf.c | 93
> ++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 119 insertions(+)
> create mode 100644 libavcodec/realtime_bsf.c
>
> diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
> index 25bbf8372b..18ddb2e52b 100644
> --- a/doc/bitstream_filters.texi
> +++ b/doc/bitstream_filters.texi
> @@ -599,6 +599,30 @@ Set Rec709 colorspace for each frame of the file
> ffmpeg -i INPUT -c copy -bsf:v
> prores_metadata=color_primaries=bt709:color_trc=bt709:colorspace=bt709
> output.mov
> @end example
>
> +@section realtime
> +
> +Slow down output processing to match real time approximately.
> +
> +This bitstream filter will pause the filtering for a variable amount of time
> +to match the output rate with the input timestamps. It is similar to the
> +@option{re} option to @code{ffmpeg}.
> +
> +It accepts the following options:
> +
> +@table @option
> +@item limit
> +Time limit for the pauses. Any pause longer than that will be considered
> +a timestamp discontinuity and reset the timer. Default is 2 seconds.
> +@item speed
> +Speed factor for processing. The value must be a float larger than zero.
> +Values larger than 1.0 will result in faster than realtime processing,
> +smaller will slow processing down. The @var{limit} is automatically adapted
> +accordingly. Default is 1.0.
> +
> +A processing speed faster than what is possible without this bitstream
> +filter cannot be achieved.
> +@end table
> +
> @section remove_extra
>
> Remove extradata from packets.
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index f37135fc07..83f143922f 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -1094,6 +1094,7 @@ OBJS-$(CONFIG_MPEG2_METADATA_BSF) +=
> mpeg2_metadata_bsf.o
> OBJS-$(CONFIG_NOISE_BSF) += noise_bsf.o
> OBJS-$(CONFIG_NULL_BSF) += null_bsf.o
> OBJS-$(CONFIG_PRORES_METADATA_BSF) += prores_metadata_bsf.o
> +OBJS-$(CONFIG_REALTIME_BSF) += realtime_bsf.o
> OBJS-$(CONFIG_REMOVE_EXTRADATA_BSF) += remove_extradata_bsf.o
> OBJS-$(CONFIG_TEXT2MOVSUB_BSF) += movsub_bsf.o
> OBJS-$(CONFIG_TRACE_HEADERS_BSF) += trace_headers_bsf.o
> diff --git a/libavcodec/bitstream_filters.c b/libavcodec/bitstream_filters.c
> index 463003966a..741a240380 100644
> --- a/libavcodec/bitstream_filters.c
> +++ b/libavcodec/bitstream_filters.c
> @@ -49,6 +49,7 @@ extern const AVBitStreamFilter ff_mov2textsub_bsf;
> extern const AVBitStreamFilter ff_noise_bsf;
> extern const AVBitStreamFilter ff_null_bsf;
> extern const AVBitStreamFilter ff_prores_metadata_bsf;
> +extern const AVBitStreamFilter ff_realtime_bsf;
> extern const AVBitStreamFilter ff_remove_extradata_bsf;
> extern const AVBitStreamFilter ff_text2movsub_bsf;
> extern const AVBitStreamFilter ff_trace_headers_bsf;
> diff --git a/libavcodec/realtime_bsf.c b/libavcodec/realtime_bsf.c
> new file mode 100644
> index 0000000000..b9abda90a4
> --- /dev/null
> +++ b/libavcodec/realtime_bsf.c
> @@ -0,0 +1,93 @@
> +/*
> + * Realtime filter
> + * Copyright (c) 2015 Nicolas George
> + * Copyright (c) 2018 Moritz Barsnick
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
> USA
> + */
> +
> +#include "libavutil/time.h"
> +#include "libavutil/opt.h"
> +#include "avcodec.h"
> +#include "bsf.h"
> +#include <float.h>
> +
> +typedef struct RealtimeContext {
> + const AVClass *class;
> + int64_t delta;
> + int64_t limit;
> + double speed;
> + unsigned inited;
> +} RealtimeContext;
> +
> +static int realtime_filter(AVBSFContext *bsf, AVPacket *pkt)
> +{
> + int ret;
> + RealtimeContext *ctx = bsf->priv_data;
> +
> + ret = ff_bsf_get_packet_ref(bsf, pkt);
> + if (ret < 0)
> + return ret;
> +
> + if (pkt->pts != AV_NOPTS_VALUE) {
> + int64_t pts = av_rescale_q(pkt->pts, bsf->time_base_in,
> AV_TIME_BASE_Q) / ctx->speed;
> + int64_t now = av_gettime_relative();
> + int64_t sleep = pts - now + ctx->delta;
> + if (!ctx->inited) {
> + ctx->inited = 1;
> + sleep = 0;
> + ctx->delta = now - pts;
If this is meant to be used for input, where seeking can take place,
wouldn't a flush() callback to set ctx->inited and ctx->delta back to 0
be needed?
> + }
> + if (FFABS(sleep) > ctx->limit / ctx->speed) {
> + av_log(ctx, AV_LOG_WARNING,
> + "time discontinuity detected: %"PRIi64" us, resetting\n",
> + sleep);
> + sleep = 0;
> + ctx->delta = now - pts;
> + }
> + if (sleep > 0) {
> + av_log(ctx, AV_LOG_DEBUG, "sleeping %"PRIi64" us\n", sleep);
> + for (; sleep > 600000000; sleep -= 600000000)
> + av_usleep(600000000);
> + av_usleep(sleep);
> + }
> + }
> +
> + return 0;
> +}
> +
> +#define OFFSET(x) offsetof(RealtimeContext, x)
> +#define FLAGS (AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_BSF_PARAM)
> +static const AVOption options[] = {
> + { "limit", "sleep time limit", OFFSET(limit), AV_OPT_TYPE_DURATION, {
> .i64 = 2000000 }, 0, INT64_MAX, FLAGS },
> + { "speed", "speed factor", OFFSET(speed), AV_OPT_TYPE_DOUBLE, { .dbl =
> 1.0 }, DBL_MIN, DBL_MAX, FLAGS },
> + { NULL },
> +};
> +
> +static const AVClass realtime_class = {
> + .class_name = "realtime_bsf",
> + .item_name = av_default_item_name,
> + .option = options,
> + .version = LIBAVUTIL_VERSION_INT,
> +};
> +
> +const AVBitStreamFilter ff_realtime_bsf = {
> + .name = "realtime",
> + .priv_data_size = sizeof(RealtimeContext),
> + .priv_class = &realtime_class,
> + .filter = realtime_filter,
> +};
> --
> 2.14.5
>
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