Author Topic: x264 configuration defaults to custom Sample Aspect Ratio  (Read 7280 times)

dumol

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x264 configuration defaults to custom Sample Aspect Ratio
« on: March 02, 2012, 10:47:05 AM »
Hi all! New user here, please bear with me. I've been using Avidemux 2.5.x to edit and transcode to MPEG4-AVC some MPEG2 TS streams. They originally have a resolution of 720x576, a Sample Aspect Ratio (SAR) of 16:15 and a Display Aspect Ratio (DAR) of 4:3. So in any decent player the video will be displayed as 768x576 (I use VLC).

By default, the result of the Avidemux conversion is a MPEG4 video with the same resolution, but a 1:1 PAR and 5:4 DAR which is rendered by VLC at 720x576, thus ruining the aspect ratio. I needed to correct this afterwards with the MP4Box utility, the only solution that I've found for Linux that doesn't require re-encoding. For the record, I had to do this: MP4Box -par 1=12:11 $video_file

Is this default "Custom" option of 1:1 for the "Sample Aspect Ratio" in the "Motion & Misc" tab of the x264 configuration window a bug or a feature? One of the reasons for being unsure is that in another thread one of the moderators has suggested that Avidemux has been made to work like that, details at http://www.avidemux.org/smf/index.php?topic=7934.msg44429#msg44429

Thanks!

dumol

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Re: x264 configuration defaults to custom Sample Aspect Ratio
« Reply #1 on: March 02, 2012, 10:53:24 AM »
Obviously, the MP4Box command was actually: MP4Box -par 1=16:15 $video_file :)

zakk

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Re: x264 configuration defaults to custom Sample Aspect Ratio
« Reply #2 on: March 02, 2012, 11:21:48 AM »
I'm not sure I understand, but I use the "PAR as input" in the x264 "Output 1" tab, and it always worked.

dumol

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Re: x264 configuration defaults to custom Sample Aspect Ratio
« Reply #3 on: March 02, 2012, 11:57:34 AM »
I'm not sure I understand, but I use the "PAR as input" in the x264 "Output 1" tab, and it always worked.

Maybe we use different versions, I don't have an "Output 1" tab in Avidemux 2.5.4 for the x264 configuration. The "Sample Aspect Ratio" section is under the "Motion & Misc" tab and I use "As Input" to keep the aspect ratio.

But the question is: why do we have to choose "as input" every time? Why is the default option one that alters the original aspect ratio? Thanks.