How to manage my customize clock (GstAudioClock) after seek/flush?

[Halley Zhao]

Hi expert:

  I have a short gst pipeline (appsrc-->videodecode-->videosink), and want to control the playback pace by an external clock.  in my simple example, I created a customized GstAudioClock basing on system time. it works for normal playback.

GstAudioClock *myGstClock = GST_AUDIO_CLOCK(gst_audio_clock_new("MyClock", (GstAudioClockGetTimeFunc)getMyClockTime, NULL/* user   data */, NULL/*GDestroyNotify destroy_notify*/));

getMyClockTime() reports played time comparable with video frame timestamp. code piece see below.

  but, I met issue after seek. 

  after seek, I simply update g_anchorTime to the seek_time (0 in my sample code); thus getMyClockTime always returns currTime comparable with timestamp of video frame.

   however video frames are dropped before seek_time. because gst_clock_get_time() always returns monotonically increasing time(not currTime as I expect).

   I tried to call gst_audio_clock_reset(myGstClock, 0), it doesn't help.

   

static uint64_t g_anchorTime = -1;
int64_t getTimeNs()
{
    struct timespec t;
    clock_gettime(CLOCK_MONOTONIC, &t);
    int64_t currTime = t.tv_sec;
    currTime = currTime * 1000*1000*1000LL + t.tv_nsec;

    return currTime;
}
GstClockTime getMyClockTime(GstClock * clock, gpointer user_data)
{
    static int dbgCount = 0;

    int64_t currTime = getTimeNs();
    currTime = currTime-g_anchorTime;
    DEBUG("dbgCount: %d, %" PRId64 ", %.3f", dbgCount++, currTime, currTime/1000/1000/1000.0);

    return currTime;

}

complete sample code see attachment seek.c

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[Halley Zhao]

my question are:

1. if it is by-design that gst_clock_get_time() reports monotonically increasing time; why video frames are blocked by basesink after seek backwards?

2. how should I 'reset' GstClock/GstAudioClock after flush/seek, I found gst_audio_reset() doesn't work as expected.

Halley Zhao <[hidden email]> 于2019年6月5日周三 下午1:49写道：

Hi expert:

  I have a short gst pipeline (appsrc-->videodecode-->videosink), and want to control the playback pace by an external clock.  in my simple example, I created a customized GstAudioClock basing on system time. it works for normal playback.

GstAudioClock *myGstClock = GST_AUDIO_CLOCK(gst_audio_clock_new("MyClock", (GstAudioClockGetTimeFunc)getMyClockTime, NULL/* user   data */, NULL/*GDestroyNotify destroy_notify*/));

getMyClockTime() reports played time comparable with video frame timestamp. code piece see below.

  but, I met issue after seek. 

  after seek, I simply update g_anchorTime to the seek_time (0 in my sample code); thus getMyClockTime always returns currTime comparable with timestamp of video frame.

   however video frames are dropped before seek_time. because gst_clock_get_time() always returns monotonically increasing time(not currTime as I expect).

   I tried to call gst_audio_clock_reset(myGstClock, 0), it doesn't help.

   

static uint64_t g_anchorTime = -1;
int64_t getTimeNs()
{
    struct timespec t;
    clock_gettime(CLOCK_MONOTONIC, &t);
    int64_t currTime = t.tv_sec;
    currTime = currTime * 1000*1000*1000LL + t.tv_nsec;

    return currTime;
}
GstClockTime getMyClockTime(GstClock * clock, gpointer user_data)
{
    static int dbgCount = 0;

    int64_t currTime = getTimeNs();
    currTime = currTime-g_anchorTime;
    DEBUG("dbgCount: %d, %" PRId64 ", %.3f", dbgCount++, currTime, currTime/1000/1000/1000.0);

    return currTime;

}

complete sample code see attachment seek.c

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