Do These Timestamps, Durations, and Offsets Look Correct??

[william.l.metcalf]

Hello All,

I am very new to Timestamps and Offsets, and I do not really know what
all problems to look for..  I have a pipeline that is essentially as
follows (the actual pipeline is in a C application)

- gst-inspect -v appsrc ! videorate ! identity ! glimagesink appsrc !
audiorate ! identity ! autoaudiosink

An excerpt of the output of the identity elements is posted below.  The
video and the audio that are produced are not in sync.  As best I can
tell from my research, gstreamer handles synchronization of video and
audio as long as the timestamps are correct.  Because my audio and video
are not synced, I am pretty sure that there must be some problem with
the timestamps below but I am not exactly sure what I am looking for.  
It seems like each timestamp = previous timestamp + duration which seems
correct to me, but I am completely clueless as to what the offset and
offset_end mean, and why they always increase.  If these timestamps are
correct, what are some other steps I can take to synchronize my audio
and video?

/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes,
timestamp: 0:00:01.234807256, duration: 0:00:00.036303855, offset:
54455, offset_end:  56056, flags: 0) 01D4C268"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.366666666, duration: 0:00:00.033333334, offset: 11,
offset_end:  12, flags: 1) 01795950"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes,
timestamp: 0:00:01.271111111, duration: 0:00:00.036326530, offset:
56056, offset_end:  57658, flags: 0) 01D4C058"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.400000000, duration: 0:00:00.033333333, offset: 12,
offset_end:  13, flags: 1) 017959A8"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes,
timestamp: 0:00:01.307437641, duration: 0:00:00.036303855, offset:
57658, offset_end:  59259, flags: 1) 01D4C000"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.433333333, duration: 0:00:00.033333333, offset: 13,
offset_end:  14, flags: 1) 01795B08"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes,
timestamp: 0:00:01.343741496, duration: 0:00:00.036326531, offset:
59259, offset_end:  60861, flags: 0) 01795F28"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.466666666, duration: 0:00:00.033333334, offset: 14,
offset_end:  15, flags: 1) 01795C10"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes,
timestamp: 0:00:01.380068027, duration: 0:00:00.036326530, offset:
60861, offset_end:  62463, flags: 0) 01795ED0"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.500000000, duration: 0:00:00.033333333, offset: 15,
offset_end:  16, flags: 1) 01795B60"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes,
timestamp: 0:00:01.416394557, duration: 0:00:00.036303855, offset:
62463, offset_end:  64064, flags: 0) 01795E78"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.533333333, duration: 0:00:00.033333333, offset: 16,
offset_end:  17, flags: 1) 01795950"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes,
timestamp: 0:00:01.452698412, duration: 0:00:00.036326531, offset:
64064, offset_end:  65666, flags: 0) 01795E20"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.566666666, duration: 0:00:00.033333334, offset: 17,
offset_end:  18, flags: 1) 01795A00"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes,
timestamp: 0:00:01.489024943, duration: 0:00:00.036303855, offset:
65666, offset_end:  67267, flags: 0) 01795DC8"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.600000000, duration: 0:00:00.033333333, offset: 18,
offset_end:  19, flags: 1) 01795A58"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity:
last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes,
timestamp: 0:00:01.525328798, duration: 0:00:00.036326530, offset:
67267, offset_end:  68869, flags: 1) 01D4C000"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity:
last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes,
timestamp: 0:00:00.633333333, duration: 0:00:00.033333333, offset: 19,
offset_end:  20, flags: 1) 01795C10"

Thank you all for your help,
William



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[Sudarshan Bisht]

As per my knowledge,  timestamp is calculated on the basis of framerate for video, for example if framerate is 30 fps then each frame will take 1/30 = 0.03333 second to get displayed i.e. called duration and to get perfect series of frames which gives real movie experience you need to consistently increase the timestamp by adding duration with previous frame's timestamp, except first frame, as its timestamp and duration will be the same.

For audio, bitrate would do the same. 

On Wed, Aug 17, 2011 at 3:33 AM, William Metcalf <[hidden email]> wrote:

Hello All,

I am very new to Timestamps and Offsets, and I do not really know what all problems to look for..  I have a pipeline that is essentially as follows (the actual pipeline is in a C application)

- gst-inspect -v appsrc ! videorate ! identity ! glimagesink appsrc ! audiorate ! identity ! autoaudiosink

An excerpt of the output of the identity elements is posted below.  The video and the audio that are produced are not in sync.  As best I can tell from my research, gstreamer handles synchronization of video and audio as long as the timestamps are correct.  Because my audio and video are not synced, I am pretty sure that there must be some problem with the timestamps below but I am not exactly sure what I am looking for.  It seems like each timestamp = previous timestamp + duration which seems correct to me, but I am completely clueless as to what the offset and offset_end mean, and why they always increase.  If these timestamps are correct, what are some other steps I can take to synchronize my audio and video?

/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes, timestamp: 0:00:01.234807256, duration: 0:00:00.036303855, offset: 54455, offset_end:  56056, flags: 0) 01D4C268"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.366666666, duration: 0:00:00.033333334, offset: 11, offset_end:  12, flags: 1) 01795950"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes, timestamp: 0:00:01.271111111, duration: 0:00:00.036326530, offset: 56056, offset_end:  57658, flags: 0) 01D4C058"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.400000000, duration: 0:00:00.033333333, offset: 12, offset_end:  13, flags: 1) 017959A8"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes, timestamp: 0:00:01.307437641, duration: 0:00:00.036303855, offset: 57658, offset_end:  59259, flags: 1) 01D4C000"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.433333333, duration: 0:00:00.033333333, offset: 13, offset_end:  14, flags: 1) 01795B08"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes, timestamp: 0:00:01.343741496, duration: 0:00:00.036326531, offset: 59259, offset_end:  60861, flags: 0) 01795F28"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.466666666, duration: 0:00:00.033333334, offset: 14, offset_end:  15, flags: 1) 01795C10"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes, timestamp: 0:00:01.380068027, duration: 0:00:00.036326530, offset: 60861, offset_end:  62463, flags: 0) 01795ED0"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.500000000, duration: 0:00:00.033333333, offset: 15, offset_end:  16, flags: 1) 01795B60"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes, timestamp: 0:00:01.416394557, duration: 0:00:00.036303855, offset: 62463, offset_end:  64064, flags: 0) 01795E78"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.533333333, duration: 0:00:00.033333333, offset: 16, offset_end:  17, flags: 1) 01795950"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes, timestamp: 0:00:01.452698412, duration: 0:00:00.036326531, offset: 64064, offset_end:  65666, flags: 0) 01795E20"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.566666666, duration: 0:00:00.033333334, offset: 17, offset_end:  18, flags: 1) 01795A00"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6404 bytes, timestamp: 0:00:01.489024943, duration: 0:00:00.036303855, offset: 65666, offset_end:  67267, flags: 0) 01795DC8"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.600000000, duration: 0:00:00.033333333, offset: 18, offset_end:  19, flags: 1) 01795A58"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTAudioIdentity: last-message = "chain   ******* (NFTAudioIdentity:sink)i (6408 bytes, timestamp: 0:00:01.525328798, duration: 0:00:00.036326530, offset: 67267, offset_end:  68869, flags: 1) 01D4C000"
/GstPipeline:NFTVideoConverter/GstIdentity:NFTVideoIdentity: last-message = "chain   ******* (NFTVideoIdentity:sink)i (699840 bytes, timestamp: 0:00:00.633333333, duration: 0:00:00.033333333, offset: 19, offset_end:  20, flags: 1) 01795C10"

Thank you all for your help,
William



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--
Regards,

Sudarshan Bisht

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