On Mon, 23 May 2005, Dik Takken wrote:
> On Mon, 23 May 2005, Steven M. Schultz wrote:
>
> > Do you see anything like that 'Deprecated X-tag' message? If you're
> > using the cvs version of mjpegtools you should see that message.
>
> Yes, I get them all the time :)
Ok - I am fairly certain I have found the cause of the problem you're
having.
What's happening is that the cvs version of mjpegtools has an "advanced
feature acceptance level" concept. Advance feature in this case
is the whole concept of alternate (other than 420jpeg) chroma samplings.
yuvscaler does NOT call 'y4m_accept_extensions(1)' because it doesn't
know about other than 420jpeg. Thus the 'XYSCSS=' tag is ignored BUT
NOT REMOVED and the chroma sampling gets defaulted to 420jpeg. That's
fine for data coming from a MJPEG card but not right for PAL-DV.
That is also why both tags are present (and possibly confusing yuvplay).
y4mscaler on the other hand does (of course ;)) enable 'advanced
features' such as multiple chroma sampling. AT THAT POINT if a 'C' tag
is present the XYSCSS= is ignored (and disgarded). IF no C tag is
present then it is created from XYSCSS= (and again the XYSCSS= is
thrown away).
Summary: other than 420jpeg (MJPEG cards) is considered an advanced
capability - something yuvscaler doesn't understand. If you're dealing
with "advanced formats" (I think a case can be made that PALDV is more
advanced, certainly current/newer than MJPEG which is what yuvscaler
understands) you need tools that can deal with the newer formats.
Hacking acceptance of other formats into yuvscaler would be a
major undertaking and that's what I think it would take to avoid
treating all 3 variants of 4:2:0 as being the same thing (which is
100% wrong).
Dealing with PALDV (PAL just _had_ to make life complicated by not
using 4:1:1 like NTSC) is a strange beast - not sure how to fix the
problem short of reinventing y4mscaler into yuvscaler.
Cheers,
Steven Schultz
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