[gst-devel] timestamps on a live h264 source

[Farkas Levente]

hi,
is there anybody how has the required knowledge about gstreamer, 
encoding and h264 to answer this question? since it's also big problem 
for us:-(

On 09/08/2009 04:28 PM, PALFFY Daniel wrote:
>
> Hi,
>
> I'm developing a gstreamer source for a raw-yuv/h264 capable video grabber
> card. In raw mode, the source works fine without setting
> GST_BUFFER_OFFSET, GST_BUFFER_OFFSET_END, GST_BUFFER_TIMESTAMP and
> GST_BUFFER_DURATION, but for h264 live play, I can't find a working
> combination.
>
> The example pipeline looks like this:
> gst-launch mysource ! "video/x-h264,framerate=25/1" ! ffdec_h264 ! xvimagesink
>
> The card provides each frame as a separate buffer, and (in the current
> configuration) I have one SPS, one PPS, one I, and 14 P-frames in a group,
> each output in a separate GstBuffer;
>
> When not setting anything, the pipeline takes all grabbed frames, but
> displays only the first (or maybe first few).
>
> If I set all the values to what i believe is correct (put a serial number
> incrementing from 0 in OFFSET, OFFSET+1 in OFFSET_END, a
> hardware-generated timestamp in TIMESTAMP, and 0 for SPS/PPS frames
> and GST_SECOND/framerate for I/P frames in DURATION), the pipeline only
> takes and displays the first four frames and then stalls.
>
> If I count the SPS/PPS frames as normal frames, use the same duration for
> them as I/P frmaes and increment the timestamp accordingly, the buffer in
> my element fills slowly as the decoder takes fewer frames than produced.
>
> When saving the stream to a file and playing back from there, everything
> works fine.
>
> What would be the correct values for the timestamps in this case? Or do I
> have to implement a clock-capable element?



-- 
   Levente                               "Si vis pacem para bellum!"