[Matroska-devel] Re: [Media-api] Design ideas for the editing system.

Steve Lhomme steve.lhomme at free.fr
Thu Jan 29 10:03:08 CET 2004


> Well I'm not sure exactly what the difference is but I'll take your word for it. Obviously we'll have to sync the control stream to the file, or vice versa actually. We know the editing stream is in sync because it defines sync. Whatever it says for a specific timecode needs to be inserted at that timecode. Even if it's just a storage file I can think we'll be wanting to play it for previewing at some point.

It's like the PNG files that Fireworks saves. You can preview them but 
it doesn't contain all the features you get when you open them with 
Fireworks. The preview is just a help, just an "accident" because they 
use a format that can actually be displayed as such.

>>BTW, that makes me think that we should be able to edit a video based on 
>>the audio timecodes, not video. So if the audio to start/stop the movie 
>>is in the middle of a video frame, we just cut the timecode of the video 
>>frame.
>>
> 
> 
> Umm... but if the audio and video are both synced what does it matter? Their control streams should have the same timecodes, just the source streams will be different. Or are you talking about when a cut falls in the middle of a video or audio frame's duration? 

Yes (very hard to edit your emails with long long lines).

> I say we enclude the whole frame of course but if control says stop then the stream stops. Otherwise pasting another stream on the end of this in the editor won't come out quite right. If the next frame is only displayed for 0.01ms then so be it, that's where the timecode said stop. If we want to do a "cut at nearest frame" that's a function that could be specified by an editor tool, and it could be audio or video, and nearest keyframe would likely be desired as well.

Cut at keyframe boundaries is a feature we need. But what I mean is 
cutting inside the frames. Sound has a bigger time resolution than 
video. And so there are more frames/samples to decide to cut. Then to 
preserve the original stream you should be able to change the length of 
a video frame depending on the one of the audio :

[  video frame  ]
[ audio samples ]
      ^
    cut here

> Yeah I'd think we might need to include that for VFR. For CFR we could assume it from the specified framerate of course.

Well the whole opint of this editor is that it can do VFR. CFR is just a 
  smaller case of VFR :)




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