[Kdenlive-devel] Audio cut "slips" from cutting point -- bug?

[jeff]

jb wrote:
> On Wednesday 21 March 2007 00.06:54 Stephane Fillod wrote:
>> Tue, Mar 20, 2007 at 11:03:05AM -0300, Fabricio Rocha skribis:
>>> My project has a lot of clips from a single .VOB file, NTSC DVD with AC3
>>> 48k audio, and lots of crossfade transitions among the clips. The
>>> transitions work OK in the timeline itself, but when I export the
>>> timeline to a video file, I notice that, while the video is correctly
>>> cut and crossfaded in the clip end, the audio from clip "A" is extended
>>> beyond the point where it should end, and only then the audio track of
>>> clip "B" starts.
>>>
>>> This causes a cumulative effect. In a certain point of the final video,
>>> the audio track was completely out of sync with the video, something
>>> like a 5 seconds delay. I tried to export to many formats, but the
>>> problem remained.
>>>
>>> Is this a known bug? Does it happen to any of you? Or am I doing
>>> something wrong?
> 
> Ok, I did some tests and it seems to me that the problem occurs if you export 
> to a format which has a different audio frequency. Can you confirm this ?
> 
> Copy the export settings from a profile that shows the bug and create a new 
> custom encoder with the same settings, but change the "frequency=" parameter 
> to match the frequency of your source video: "frequency=48000".
> 
> Let me know if export works fine that way...

I have a series of jpegs with two audio tracks on a 15 minute timeline with a 
few fade ins & outs using "volume" effect. I'm exporting to NTSC DVD. I 
converted all the audio files to 48000 Hz wavs using sr-convert (.sf.net).

I get a pretty significant shift in time--like a few seconds after a few 
minutes of audio.

I did a custom export to .vob using this (using stock DVD NTSC export and 
adding "frequency=48000"):

format=dvd vcodec=mpeg2video acodec=ac3 size=720x480 video_bit_rate=6000000 
video_rc_max_rate=9000000 video_rc_min_rate=0 video_rc_buffer_size=1835008 
mux_packet_size=2048 mux_rate=10080000 audio_bit_rate=192000 
audio_sample_rate=48000 frame_size=720x480 frame_rate=30000/1001 gop_size=18 
me_range=63 frequency=48000

It did not appear to have any effect--in other words, there is still a 
significant time lag. The images get ahead of the audio. When playing in the 
timeline things are fine.

Thanks for kdenlive, I'm really enjoying it. :)

-Jeff