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https://github.com/FFmpeg/FFmpeg.git
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v4l2: allow to convert monotonic timestamps.
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parent
8a9ae37fee
commit
12292f35a3
2
configure
vendored
2
configure
vendored
@ -1157,6 +1157,7 @@ HAVE_LIST="
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attribute_may_alias
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attribute_packed
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cbrtf
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clock_gettime
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closesocket
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cmov
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dcbzl
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@ -3048,6 +3049,7 @@ fi
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# Solaris has nanosleep in -lrt, OpenSolaris no longer needs that
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check_func nanosleep || { check_func nanosleep -lrt && add_extralibs -lrt; }
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check_func clock_gettime || { check_func clock_gettime -lrt && add_extralibs -lrt; }
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check_func fcntl
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check_func fork
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check_func getaddrinfo $network_extralibs
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@ -520,6 +520,13 @@ supported using @command{-list_formats all} for Video4Linux2 devices.
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Some usage examples of the video4linux2 devices with ffmpeg and ffplay:
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The time base for the timestamps is 1 microsecond. Depending on the kernel
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version and configuration, the timestamps may be derived from the real time
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clock (origin at the Unix Epoch) or the monotonic clock (origin usually at
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boot time, unaffected by NTP or manual changes to the clock). The
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@option{-timestamps abs} or @option{-ts abs} option can be used to force
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conversion into the real time clock.
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Note that if FFmpeg is build with v4l-utils support ("--enable-libv4l2"
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option), it will always be used.
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@example
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@ -28,7 +28,7 @@ OBJS-$(CONFIG_PULSE_INDEV) += pulse.o
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OBJS-$(CONFIG_SDL_OUTDEV) += sdl.o
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OBJS-$(CONFIG_SNDIO_INDEV) += sndio_common.o sndio_dec.o
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OBJS-$(CONFIG_SNDIO_OUTDEV) += sndio_common.o sndio_enc.o
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OBJS-$(CONFIG_V4L2_INDEV) += v4l2.o
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OBJS-$(CONFIG_V4L2_INDEV) += v4l2.o timefilter.o
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OBJS-$(CONFIG_V4L_INDEV) += v4l.o
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OBJS-$(CONFIG_VFWCAP_INDEV) += vfwcap.o
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OBJS-$(CONFIG_X11_GRAB_DEVICE_INDEV) += x11grab.o
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@ -51,6 +51,7 @@
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#include "libavutil/log.h"
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#include "libavutil/opt.h"
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#include "avdevice.h"
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#include "timefilter.h"
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#include "libavutil/parseutils.h"
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#include "libavutil/pixdesc.h"
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#include "libavutil/avstring.h"
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@ -73,6 +74,28 @@ static const int desired_video_buffers = 256;
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#define V4L_RAWFORMATS 1
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#define V4L_COMPFORMATS 2
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/**
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* Return timestamps to the user exactly as returned by the kernel
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*/
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#define V4L_TS_DEFAULT 0
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/**
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* Autodetect the kind of timestamps returned by the kernel and convert to
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* absolute (wall clock) timestamps.
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*/
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#define V4L_TS_ABS 1
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/**
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* Assume kernel timestamps are from the monotonic clock and convert to
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* absolute timestamps.
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*/
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#define V4L_TS_MONO2ABS 2
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/**
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* Once the kind of timestamps returned by the kernel have been detected,
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* the value of the timefilter (NULL or not) determines whether a conversion
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* takes place.
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*/
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#define V4L_TS_CONVERT_READY V4L_TS_DEFAULT
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struct video_data {
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AVClass *class;
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int fd;
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@ -81,6 +104,9 @@ struct video_data {
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int frame_size;
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int interlaced;
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int top_field_first;
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int ts_mode;
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TimeFilter *timefilter;
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int64_t last_time_m;
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int buffers;
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void **buf_start;
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@ -455,6 +481,66 @@ static void mmap_release_buffer(AVPacket *pkt)
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pkt->size = 0;
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}
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#if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
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static int64_t av_gettime_monotonic(void)
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{
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struct timespec tv;
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clock_gettime(CLOCK_MONOTONIC, &tv);
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return (int64_t)tv.tv_sec * 1000000 + tv.tv_nsec / 1000;
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}
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#endif
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static int init_convert_timestamp(AVFormatContext *ctx, int64_t ts)
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{
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struct video_data *s = ctx->priv_data;
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int64_t now;
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now = av_gettime();
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if (s->ts_mode == V4L_TS_ABS &&
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ts <= now + 1 * AV_TIME_BASE && ts >= now - 10 * AV_TIME_BASE) {
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av_log(ctx, AV_LOG_INFO, "Detected absolute timestamps\n");
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s->ts_mode = V4L_TS_CONVERT_READY;
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return 0;
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}
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#if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
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now = av_gettime_monotonic();
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if (s->ts_mode == V4L_TS_MONO2ABS ||
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(ts <= now + 1 * AV_TIME_BASE && ts >= now - 10 * AV_TIME_BASE)) {
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int64_t period = av_rescale_q(1, ctx->streams[0]->codec->time_base,
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AV_TIME_BASE_Q);
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av_log(ctx, AV_LOG_INFO, "Detected monotonic timestamps, converting\n");
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/* microseconds instead of seconds, MHz instead of Hz */
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s->timefilter = ff_timefilter_new(1, period, 1.0E-6);
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s->ts_mode = V4L_TS_CONVERT_READY;
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return 0;
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}
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#endif
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av_log(ctx, AV_LOG_ERROR, "Unknown timestamps\n");
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return AVERROR(EIO);
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}
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static int convert_timestamp(AVFormatContext *ctx, int64_t *ts)
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{
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struct video_data *s = ctx->priv_data;
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if (s->ts_mode) {
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int r = init_convert_timestamp(ctx, *ts);
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if (r < 0)
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return r;
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}
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#if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
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if (s->timefilter) {
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int64_t nowa = av_gettime();
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int64_t nowm = av_gettime_monotonic();
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ff_timefilter_update(s->timefilter, nowa, nowm - s->last_time_m);
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s->last_time_m = nowm;
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*ts = ff_timefilter_eval(s->timefilter, *ts - nowm);
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}
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#endif
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return 0;
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}
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static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
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{
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struct video_data *s = ctx->priv_data;
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@ -490,6 +576,9 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
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pkt->data= s->buf_start[buf.index];
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pkt->size = buf.bytesused;
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pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
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res = convert_timestamp(ctx, &pkt->pts);
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if (res < 0)
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return res;
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pkt->destruct = mmap_release_buffer;
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buf_descriptor = av_malloc(sizeof(struct buff_data));
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if (buf_descriptor == NULL) {
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@ -847,6 +936,11 @@ static const AVOption options[] = {
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{ "all", "Show all available formats", OFFSET(list_format), AV_OPT_TYPE_CONST, {.dbl = V4L_ALLFORMATS }, 0, INT_MAX, DEC, "list_formats" },
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{ "raw", "Show only non-compressed formats", OFFSET(list_format), AV_OPT_TYPE_CONST, {.dbl = V4L_RAWFORMATS }, 0, INT_MAX, DEC, "list_formats" },
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{ "compressed", "Show only compressed formats", OFFSET(list_format), AV_OPT_TYPE_CONST, {.dbl = V4L_COMPFORMATS }, 0, INT_MAX, DEC, "list_formats" },
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{ "timestamps", "Kind of timestamps for grabbed frames", OFFSET(ts_mode), AV_OPT_TYPE_INT, {.dbl = 0 }, 0, 2, DEC, "timestamps" },
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{ "default", "Use timestamps from the kernel", OFFSET(ts_mode), AV_OPT_TYPE_CONST, {.dbl = V4L_TS_DEFAULT }, 0, 2, DEC, "timestamps" },
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{ "abs", "Use absolute timestamps (wall clock)", OFFSET(ts_mode), AV_OPT_TYPE_CONST, {.dbl = V4L_TS_ABS }, 0, 2, DEC, "timestamps" },
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{ "mono2abs", "Force conversion from monotonic to absolute timestamps", OFFSET(ts_mode), AV_OPT_TYPE_CONST, {.dbl = V4L_TS_MONO2ABS }, 0, 2, DEC, "timestamps" },
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{ "ts", "Kind of timestamps for grabbed frames", OFFSET(ts_mode), AV_OPT_TYPE_INT, {.dbl = 0 }, 0, 2, DEC, "timestamps" },
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{ NULL },
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};
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