[mythtv] mythtv commit: r8651 by danielk (Auto Aspect Ratio transcode)

Dave Just justifiably at cwazy.co.uk
Thu Jan 19 23:18:28 UTC 2006

Yes!   This is just the situation I had.  I have my low quality  
transcode settings to rescale from usual capture resolution of  
720x576 down to 480x384.  Both multiples of 16.  But then I also  
added the "Preserve aspect option" when it appeared.  The result was  
that some of my captures which are at 4:3 instead of 16:9 got scaled  
to a larger height, 392, not divisible by 16... and yes, the  
transcoded files have fuzzy green borders in the top 1/6th or so.

I'm disabling the "preserve aspect ratio" for now again.  Maybe that  
option needs tuning to enforce the standards.  (BTW, wouldn't it be  
better to scale the width according to the desired height anyway?  I  
think it's more useful to specify vertical resolution to match output  

  - Dave

On 19 Jan 2006, at 22:42, Endaf Jones wrote:

>> Modified:
>>   trunk/mythtv/libs/libmythtv/videobuffers.cpp
>> Log:
>> Fixes #1053.
>> In this case an MPEG-4 recording is using a frame height which is not
>> a multiple of 16. ffmpeg isn't doing any validation on the dimensions
>> so it ends up writing outside the buffer. This just pads allocated
>> buffers up to multiples of 16, so that this type of error doesn't  
>> cause
>> a segfault with any of the codecs we support. MythTV does prevent you
>> from setting an invalid dimension when you record to a MPEG-4 NUV, so
>> AFAIK this is more of a legacy issue.
> Question..
> What about transcoding MPEG2 into MPEG4 after a recording and you have
> "Resize Video while transcoding" AND the newly developed "Preserve
> Aspect Ratio of Video when resizing" option?  The height is auto
> calculated in that case.
> Is this situation the same as the above commit?
> I say this because I have a PBS HDTV program 1920x1080i that I
> transcode into a 544 wide MPEG4 so I can view it on my SDTV.  The
> height works out to be 302 or so pixels (to keep the aspect correct).
> When I play that newly encoded file, I have a strange color cast on
> the top 1/6th of the picture.
> Same problem or different?
> --
> # Endaf
> _______________________________________________
> mythtv-dev mailing list
> mythtv-dev at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev
> !DSPAM:43d01670110879830010231!

More information about the mythtv-dev mailing list