[FFmpeg-devel] [PATCH] v4l2: allow to convert monotonic timestamps.
Luca Abeni
lucabe72 at email.it
Mon Apr 2 11:13:49 CEST 2012
Hi,
this version looks good to me, thanks for updating the patch!
When committing, you can add some comments on the definitions of V4L_TS_DEFAULT
(BTW, the _RAW name looked more intuitive to me, but it's ok), V4L_TS_ABS,
and V4L_TS_MONO2ABS, explaining their meanings.
Thanks,
Luca
On 04/01/2012 07:42 PM, Nicolas George wrote:
> Signed-off-by: Nicolas George<nicolas.george at normalesup.org>
> ---
> configure | 2 +
> doc/indevs.texi | 7 ++++
> libavdevice/Makefile | 2 +-
> libavdevice/v4l2.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 93 insertions(+), 1 deletions(-)
>
> diff --git a/configure b/configure
> index 1eb8e92..1b75390 100755
> --- a/configure
> +++ b/configure
> @@ -1157,6 +1157,7 @@ HAVE_LIST="
> attribute_may_alias
> attribute_packed
> cbrtf
> + clock_gettime
> closesocket
> cmov
> dcbzl
> @@ -3048,6 +3049,7 @@ fi
> # Solaris has nanosleep in -lrt, OpenSolaris no longer needs that
> check_func nanosleep || { check_func nanosleep -lrt&& add_extralibs -lrt; }
>
> +check_func clock_gettime || { check_func clock_gettime -lrt&& add_extralibs -lrt; }
> check_func fcntl
> check_func fork
> check_func getaddrinfo $network_extralibs
> diff --git a/doc/indevs.texi b/doc/indevs.texi
> index f41c1cb..e699e11 100644
> --- a/doc/indevs.texi
> +++ b/doc/indevs.texi
> @@ -520,6 +520,13 @@ supported using @command{-list_formats all} for Video4Linux2 devices.
>
> Some usage examples of the video4linux2 devices with ffmpeg and ffplay:
>
> +The time base for the timestamps is 1 microsecond. Depending on the kernel
> +version and configuration, the timestamps may be derived from the real time
> +clock (origin at the Unix Epoch) or the monotonic clock (origin usually at
> +boot time, unaffected by NTP or manual changes to the clock). The
> + at option{-timestamps abs} or @option{-ts abs} option can be used to force
> +conversion into the real time clock.
> +
> Note that if FFmpeg is build with v4l-utils support ("--enable-libv4l2"
> option), it will always be used.
> @example
> diff --git a/libavdevice/Makefile b/libavdevice/Makefile
> index d7806ea..7f0c1d3 100644
> --- a/libavdevice/Makefile
> +++ b/libavdevice/Makefile
> @@ -28,7 +28,7 @@ OBJS-$(CONFIG_PULSE_INDEV) += pulse.o
> OBJS-$(CONFIG_SDL_OUTDEV) += sdl.o
> OBJS-$(CONFIG_SNDIO_INDEV) += sndio_common.o sndio_dec.o
> OBJS-$(CONFIG_SNDIO_OUTDEV) += sndio_common.o sndio_enc.o
> -OBJS-$(CONFIG_V4L2_INDEV) += v4l2.o
> +OBJS-$(CONFIG_V4L2_INDEV) += v4l2.o timefilter.o
> OBJS-$(CONFIG_V4L_INDEV) += v4l.o
> OBJS-$(CONFIG_VFWCAP_INDEV) += vfwcap.o
> OBJS-$(CONFIG_X11_GRAB_DEVICE_INDEV) += x11grab.o
> diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c
> index 642df1d..491bc85 100644
> --- a/libavdevice/v4l2.c
> +++ b/libavdevice/v4l2.c
> @@ -51,6 +51,7 @@
> #include "libavutil/log.h"
> #include "libavutil/opt.h"
> #include "avdevice.h"
> +#include "timefilter.h"
> #include "libavutil/parseutils.h"
> #include "libavutil/pixdesc.h"
> #include "libavutil/avstring.h"
> @@ -73,6 +74,15 @@ static const int desired_video_buffers = 256;
> #define V4L_RAWFORMATS 1
> #define V4L_COMPFORMATS 2
>
> +#define V4L_TS_DEFAULT 0
> +#define V4L_TS_ABS 1
> +#define V4L_TS_MONO2ABS 2
> +
> +/* Once the kind of timestamps returned by the kernel have been detected,
> + the value of the timefilter (NULL or not) determines whether a conversion
> + takes place. */
> +#define V4L_TS_CONVERT_READY V4L_TS_DEFAULT
> +
> struct video_data {
> AVClass *class;
> int fd;
> @@ -81,6 +91,9 @@ struct video_data {
> int frame_size;
> int interlaced;
> int top_field_first;
> + int ts_mode;
> + TimeFilter *timefilter;
> + int64_t last_time_m;
>
> int buffers;
> void **buf_start;
> @@ -455,6 +468,68 @@ static void mmap_release_buffer(AVPacket *pkt)
> pkt->size = 0;
> }
>
> +#if HAVE_CLOCK_GETTIME&& defined(CLOCK_MONOTONIC)
> +static int64_t av_gettime_monotonic(void)
> +{
> + struct timespec tv;
> +
> + clock_gettime(CLOCK_MONOTONIC,&tv);
> + return (int64_t)tv.tv_sec * 1000000 + tv.tv_nsec / 1000;
> +}
> +#endif
> +
> +static int init_convert_timestamp(AVFormatContext *ctx, int64_t ts)
> +{
> + struct video_data *s = ctx->priv_data;
> + int64_t now;
> +
> + now = av_gettime();
> + if (s->ts_mode == V4L_TS_ABS&&
> + ts<= now + 1 * AV_TIME_BASE&& ts>= now - 10 * AV_TIME_BASE) {
> + av_log(ctx, AV_LOG_INFO, "Detected absolute timestamps\n");
> + s->ts_mode = V4L_TS_CONVERT_READY;
> + return 0;
> + }
> +#if HAVE_CLOCK_GETTIME&& defined(CLOCK_MONOTONIC)
> + now = av_gettime_monotonic();
> + if (s->ts_mode == V4L_TS_MONO2ABS ||
> + (ts<= now + 1 * AV_TIME_BASE&& ts>= now - 10 * AV_TIME_BASE)) {
> + int64_t period = av_rescale_q(1, ctx->streams[0]->codec->time_base,
> + AV_TIME_BASE_Q);
> + av_log(ctx, AV_LOG_INFO, "Detected monotonic timestamps, converting\n");
> + /* microseconds instead of seconds, MHz instead of Hz */
> + s->timefilter = ff_timefilter_new(1, period, 1.0E-6);
> + s->ts_mode = V4L_TS_CONVERT_READY;
> + return 0;
> + }
> +#endif
> + av_log(ctx, AV_LOG_ERROR, "Unknown timestamps\n");
> + return AVERROR(EIO);
> +}
> +
> +static int convert_timestamp(AVFormatContext *ctx, int64_t *ts)
> +{
> + struct video_data *s = ctx->priv_data;
> +
> + if (s->ts_mode) {
> + int r = init_convert_timestamp(ctx, *ts);
> + if (r< 0)
> + return r;
> + }
> +#if HAVE_CLOCK_GETTIME&& defined(CLOCK_MONOTONIC)
> + if (s->timefilter) {
> + int64_t nowa = av_gettime();
> + int64_t nowm = av_gettime_monotonic();
> + int64_t t = *ts;
> + ff_timefilter_update(s->timefilter, nowa, nowm - s->last_time_m);
> + s->last_time_m = nowm;
> + *ts = ff_timefilter_eval(s->timefilter, *ts - nowm);
> + av_log(0, 16, "%ld -> %ld \n", t, *ts);
> + }
> +#endif
> + return 0;
> +}
> +
> static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
> {
> struct video_data *s = ctx->priv_data;
> @@ -490,6 +565,9 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
> pkt->data= s->buf_start[buf.index];
> pkt->size = buf.bytesused;
> pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
> + res = convert_timestamp(ctx,&pkt->pts);
> + if (res< 0)
> + return res;
> pkt->destruct = mmap_release_buffer;
> buf_descriptor = av_malloc(sizeof(struct buff_data));
> if (buf_descriptor == NULL) {
> @@ -847,6 +925,11 @@ static const AVOption options[] = {
> { "all", "Show all available formats", OFFSET(list_format), AV_OPT_TYPE_CONST, {.dbl = V4L_ALLFORMATS }, 0, INT_MAX, DEC, "list_formats" },
> { "raw", "Show only non-compressed formats", OFFSET(list_format), AV_OPT_TYPE_CONST, {.dbl = V4L_RAWFORMATS }, 0, INT_MAX, DEC, "list_formats" },
> { "compressed", "Show only compressed formats", OFFSET(list_format), AV_OPT_TYPE_CONST, {.dbl = V4L_COMPFORMATS }, 0, INT_MAX, DEC, "list_formats" },
> + { "timestamps", "Kind of timestamps for grabbed frames", OFFSET(ts_mode), AV_OPT_TYPE_INT, {.dbl = 0 }, 0, 2, DEC, "timestamps" },
> + { "default", "Use timestamps from the kernel", OFFSET(ts_mode), AV_OPT_TYPE_CONST, {.dbl = V4L_TS_DEFAULT }, 0, 2, DEC, "timestamps" },
> + { "abs", "Use absolute timestamps (wall clock)", OFFSET(ts_mode), AV_OPT_TYPE_CONST, {.dbl = V4L_TS_ABS }, 0, 2, DEC, "timestamps" },
> + { "mono2abs", "Force conversion from monotonic to absolute timestamps", OFFSET(ts_mode), AV_OPT_TYPE_CONST, {.dbl = V4L_TS_MONO2ABS }, 0, 2, DEC, "timestamps" },
> + { "ts", "Kind of timestamps for grabbed frames", OFFSET(ts_mode), AV_OPT_TYPE_INT, {.dbl = 0 }, 0, 2, DEC, "timestamps" },
> { NULL },
> };
>
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