[FFmpeg-devel] [PATCH 1/3] avdevice/dshow: implement option to use device video timestamps

[Diederick Niehorster]

The dshow plugin ignores timestamps for video frames provided by the DirectShow device, instead using wallclock time, apparently because the implementer of this code had a device that provided unreliable timestamps. Me (and others) would like to use the device's timestamps. The new use_video_device_timestamps option for dshow device enables them to do so. Since the majority of video devices out there probably provide fine timestamps, this patch sets the default to using the device timestamps, which means best fidelity timestamps are used by default. Using the new option, the user can switch this off and revert to the old behavior, so a fall back remains available in case the device provides broken timestamps.

Solves trac #8620.

Signed-off-by: Diederick Niehorster <dcnieho at gmail.com>
---
 libavdevice/dshow.c         |  1 +
 libavdevice/dshow_capture.h |  1 +
 libavdevice/dshow_pin.c     | 13 +++++++------
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/libavdevice/dshow.c b/libavdevice/dshow.c
index 8d0a6fcc09..2e9f9ddf3f 100644
--- a/libavdevice/dshow.c
+++ b/libavdevice/dshow.c
@@ -1317,6 +1317,7 @@ static const AVOption options[] = {
     { "audio_device_save", "save audio capture filter device (and properties) to file", OFFSET(audio_filter_save_file), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
     { "video_device_load", "load video capture filter device (and properties) from file", OFFSET(video_filter_load_file), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
     { "video_device_save", "save video capture filter device (and properties) to file", OFFSET(video_filter_save_file), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
+    { "use_video_device_timestamps", "use device instead of wallclock timestamps for video frames", OFFSET(use_video_device_timestamps), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, DEC },
     { NULL },
 };
 
diff --git a/libavdevice/dshow_capture.h b/libavdevice/dshow_capture.h
index 06ded2ba96..5a2691518c 100644
--- a/libavdevice/dshow_capture.h
+++ b/libavdevice/dshow_capture.h
@@ -312,6 +312,7 @@ struct dshow_ctx {
     char *audio_filter_save_file;
     char *video_filter_load_file;
     char *video_filter_save_file;
+    int   use_video_device_timestamps;
 
     IBaseFilter *device_filter[2];
     IPin        *device_pin[2];
diff --git a/libavdevice/dshow_pin.c b/libavdevice/dshow_pin.c
index 3dae405e65..ee0d4a1b42 100644
--- a/libavdevice/dshow_pin.c
+++ b/libavdevice/dshow_pin.c
@@ -309,12 +309,16 @@ long ff_dshow_meminputpin_Receive(DShowMemInputPin *this, IMediaSample *sample)
     if (!sample)
         return E_POINTER;
 
+    priv_data = pin->filter->priv_data;
+    s = priv_data;
+    ctx = s->priv_data;
+
     IMediaSample_GetTime(sample, &orig_curtime, &dummy);
     orig_curtime += pin->filter->start_time;
     IReferenceClock_GetTime(clock, &graphtime);
-    if (devtype == VideoDevice) {
-        /* PTS from video devices is unreliable. */
-        IReferenceClock_GetTime(clock, &curtime);
+    if (devtype == VideoDevice && !ctx->use_video_device_timestamps) {
+            /* PTS from video devices is unreliable. */
+            IReferenceClock_GetTime(clock, &curtime);
     } else {
         IMediaSample_GetTime(sample, &curtime, &dummy);
         if(curtime > 400000000000000000LL) {
@@ -330,9 +334,6 @@ long ff_dshow_meminputpin_Receive(DShowMemInputPin *this, IMediaSample *sample)
 
     buf_size = IMediaSample_GetActualDataLength(sample);
     IMediaSample_GetPointer(sample, &buf);
-    priv_data = pin->filter->priv_data;
-    s = priv_data;
-    ctx = s->priv_data;
     index = pin->filter->stream_index;
 
     av_log(NULL, AV_LOG_VERBOSE, "dshow passing through packet of type %s size %8d "
-- 
2.28.0.windows.1