Difference between revisions of "Avidemux"

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You must press <V Process> to actually do the transcoding.
 
You must press <V Process> to actually do the transcoding.
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[[Category:HOWTO]]

Revision as of 02:54, 2 December 2005

This is PVR350 specific

Settings

Set the Outp. fmt to <Mpeg A+V>

This tells avidemux to just pass the DVD through without altering it (apart from the cut points obviously). It should take just 1-5 minutes to save a few Gb nuv.

Editing

Basically:

  • record using DVD profile on PVRx50
  • move the nuv file to your editing space
  • use avidemux (2.36, not 2.38) to index and cut out commercials (5 mins)
  • optionally use avidemux to save screenshots (press 'j') (1 min - 20 mins depending on fussiness)
  • save as mpeg (A+V) into show.VOB (5 mins)
  • use qdvdauthor to create menu (5 mins)
  • save as VIDEO_TS (10 mins)
  • burn to DVD (15 mins)
  • optionally use gimp to create cover (hours and hours if you get fancy!!)

Removing a section (advert)

  • Scroll through to where you want the cut to start
  • Now hit the A button to mark the selection-start. This can be on any frame type (at least I've never had a problem)
  • Click through to the end of the advert (I click to the right of the slider in the scroll bar to get a rough place - much quicker than using the keyframe advance)
  • Now, click to the next (or previous) keyframe.
  • Now use the B button to mark the selection-end
  • Hit Delete

Trimming a file (removing leading credits)

  • Go to the first frame
  • Now hit the A button to mark the selection-start
  • Scroll to the frame you want as the first frame
  • Now, click to the next (or previous) keyframe
  • Now use the B button to mark the selection-end
  • Hit Delete

Trimming a file (removing trailing credits)

  • Scroll to the frame you want as the last frame
  • Now, click to the next (or previous) keyframe
  • Now, advance 1 frame (press '6') --- This is important on older versions of avidemux.
  • Now hit the A button
  • Advance to the last frame and hit the B button
  • Hit Delete

Notes:

  • I never use the find black frame - too slow.
  • dragging the slider in the scrollbar is actually really good!!

The reason for the frame advance is that the last frame must be a keyframe (or avidemux complains). If you put your 'cursor' on a keyframe, and mark it as the A-point, avidemux deletes from-and-including the A-point.

The reason for all this is to do with the way mpeg holds video. You know how cine film is a series of still images played one after the other. Well mpeg does have still images (a keyframe or I-frame) and then it stores the changes between that still image and the next frame. These frames are called P-frames or B-frames and they don't contain images, just info about the bits of the image that have changed. This is how mpeg does compression.

So imagine you're going through the video and you show a picture. Then you add a bit of red here and take away some green there... and you get the next picture. Do this 12 times or so. Eventually, just in case a glitch crept in, we have another keyframe.

OK, now do it again... show a keyframe and then make some changes, then more changes. Now, imagine we've cut a section so skip ahead in the video to a random B- or P-frame. This frame contains changes - but they're for a completely different image. So if you apply these changes you end up with a pixellated multicolour screen for a few frames (until a new I-frame appears).

Cory Papenfuss noted:
I would just like to add again that this procedure only works 95% of the time for broadcast/cable captures... about 80% of the time for tape transfers. Avidemux cannot deal with chaining A/V sync throughout the file, and this method will have broken sync with one of these unfortunate captures. The author of avidemux acknowleges this limitation, but says a fair bit of internal work would be needed to fix it.

Advanced Editing

Trimming the top+bottom black bars and saving a film as a 16:9 DVD

In the Video section choose 'DVD'. Then press <Configure> and select encoding type Quantizer, and set the value to 4. Since we'll resize the movie to 16:9 this is where you set the aspect ratio that you want the output played at.

You must press <V Process> to actually do the transcoding.