interesting VEGAS 8 render problem

[compusic]

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. 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?


thanks.

[aedipuss]

i'm not sure it was ever an ieee requirement to be based that way but an encoder adjustment so no part of the video wasn't compressed/motion compensated. try comparing the sizes of a 270 vs 272 encodes and i'll bet the 270 is bigger because of the "non-standard" size.

mpeg4 simple profile is 16x16 based but other profiles allow down to 4x4 macroblocks requiring higher bitrates.

[compusic]

thanks for reply. I'm afraid that's not the cause.
even 270 is not integer times of 4.

[Midzuki]

Depending on the codec (and depending on the application that uses it),
only the width must be an integer multiple of 4, whereas the height
must be just a multiple of 2.