Posted: Sat 8 Mar 2008, 5:51 Post subject: An interesting VEGAS 8 render problem
we know that a encoder based on MPEG compressing technology requires that video frame's pixel number should be integer times of 16. For example a 480X272 video frame, both 480 and 272 are integer times of 16.
for vegas 7 and previous version, for a 480X270 project ( a 16:9 project), if I want to render the video using mp4 or 264 encoder, even I set the frame to 480X270 in the encoder's setting tab, the encoder will change the frame to 480X272, adding 2 extra balck lines. I thought I knew why, since it's a MPEG encoder.
but waite, now the same project in VEGAS 8, render using mp4 or 264 encoder, if I set the output frame to 480X270 in the encoder, the encoder will not change it. the rendered video is definitely 480X270! I have cheked it using Gspot.
then why? how can this happen? does VEGAS 8 have another advanced encoder? or the MPEG compressing standard has changed or improved?
Joined: 04 Feb 2003 Posts: 583 Location: Lisboa, Portugal
Posted: Sat 8 Mar 2008, 19:36 Post subject:
The stream can be encoded internally with 272 lines, but the header can state that only 270 lines contain real video. In other words, the size used by the encoding algorithm does not have to be the same size that is displayed on the screen.
The same thing happens with JPEG files, for example (they work with 8x8 pixel blocks, but there's no reason why the displayed image dimensions must be a multiple of 8 ).
For some reason, some encoders don't support this, but I think it has always been "legal" according to the standard.
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