Re: MPEG-1 aspect ratio constants fix

Bernhard Praschinger wrote:
> Hallo
> 
> 
> Linards Ticmanis wrote:
>> There seem to be two wrong values in the MPEG-1 aspect ratio constants
>> used by mjpeg_play; i'm attaching a diff with these ones changed.
>> 
>> The majority of sources I found on-line agree on a set of values not
>> completely alike to the one used in mjpeg_play. This includes the source
>> of mplayer and a lot of web pages (a few have the values currently in
>> the source). Unfortunately I don't have access to the original MPEG
>> standard documents. If you have, could you check this?
>> 
>> Mathematically the values given here make more sense than the ones
>> currently in the source; with these new values, 352x240 becomes 321x240
>> on playback, which is much closer to 4:3 than the 313x240 you get with
>> the values currently in the source.
> Are you sure that these fields make it into the final mpeg ?
> I have searched around and didn't find any hint about the values.

Hmmm... Seems like the numerical constants in fact aren't currently used
in the source. There's a function to guess the correct aspect code from
the values that arrive in the yuv4mpeg input, however it is always the
MPEG-2 aspect code that is calculated with that function, then the
MPEG-1 aspect code is rough-guessed from that. Of course the string
constants are used, but only in informative output. So unless and until
you a) care for very correct informative output, or b) modify the source
to actually guess MPEG-1 aspect codes directly, this is indeed a purely
cosmetic issue.

As for the values, a Google search - simply using several of the
numerical values together, obviously not the ones that differ between
the two lists - will turn up a number of pages that have the list of
constants. Most seem to agree on the values I gave. I can mail a list of
some pages if you like. As I said, I have no access to the original
standard documents.

-- 
Linards Ticmanis

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