Feature request: Add seek by time stamp

[Jie-Fang]

Hi Roman,
Could you add a feature of seeking frame by time stamp. It can be used on variable frame rate videos.
Thanks!

[rarzumanyan]

Hi @Jie-Fang

Please check out branch issue_232, I've added seek by timestamp. Here is how you can use it:

decoder = dec.NvDecoder(gpu_id, input, dec_file, dec.InitMode.BUILTIN)

# Will seek to 13th second of video
decoder.seek(13, nvc.SeekMode.PREV_KEY_FRAME, nvc.SeekCriteria.BY_TIMESTAMP)
decoder.decode(frames_to_decode = 16, verbose=True)

It doesn't break existing API, all your previous calls to Seek without nvc.SeekCriteria will act as before (seek by frame number).
I've checked this new method on my machine, it works fine.
Please test it thoroughly and confirm if I can merge feature branch to master.

[Jie-Fang]

Hi Roman,

Sorry for replying late.
I have tested this feature, it works well when I set the timestamp less than video duration.
But if I set timestamp exceeds the video length, the VPF print Failed to read frame: End of file infinitely and can't kill the process(I run it in a docker container). FFmpeg will print the timestamp is invalid. So I think VPF should throw this info if the timestamp is invalid and stops executing.

[rarzumanyan]

Thanks for the update, @Jie-Fang

You're right, there was a bug which caused decoder to flush in infinite loop. It's fixed and pushed to issue_232.
Following code now works fine and doesn't cause infinite loop:

decoder = dec.NvDecoder(gpu_id, input, output, dec.InitMode.BUILTIN)

# Seeking for frame with timestamp of 65536 seconds which is more then input video length.
decoder.seek(seek_frame=65536, seek_mode=nvc.SeekMode.PREV_KEY_FRAME,
 seek_criteria=nvc.SeekCriteria.BY_TIMESTAMP)

decoder.decode(frames_to_decode = 256, verbose=True)
num_frames = decoder.dec_frames()
print (str(num_frames), ' frames decoded.')

Outputs:

Decoding on GPU 0
Seeking for the frame 65536
Failed to read frame: End of file
Failed to read frame: End of file
Failed to read frame: End of file
Failed to read frame: End of file
Failed to read frame: End of file
0 frames decoded.
Checking token allocation counters: No leaks dectected

In the end of decoding loop, decoder submits 5 empty frames because it's the size of queue, don't worry about that. It does not reconstruct a single frame as it's said in the output.

[Jie-Fang]

It's fixed and works well now, thanks Roman!

[rarzumanyan]

You're welcome!
Closing and fixed and merging to master.