[FFmpeg-user] Decoding Raw YUV Frames From MPEG2

[Stu]

Andy

Alright, was concerned as I wanted to resize the stream and thought that it might lead to more out of spec variance.

Thanks for looking into this for me. :)

Regards

--------
Stu


--- On Sat, 2/2/13, Andy Furniss <andyqos at ukfsn.org> wrote:

> From: Andy Furniss <andyqos at ukfsn.org>
> Subject: Re: [FFmpeg-user] Decoding Raw YUV Frames From MPEG2
> To: "FFmpeg user questions" <ffmpeg-user at ffmpeg.org>
> Cc: "Stu" <mario753 at yahoo.com>
> Date: Saturday, 2 February, 2013, 20:47
> Stu wrote:
> > Andy
> > 
> >> How far out are they?
> > 
> > Frequency analysis graph shows three spikes, at values
> 16, 128 and 234.
> > But the full range is present, 0 accounting for over
> 32,000 samples and 255 for over 8,000.
> > 
> > Is this what is usually passed to a hardware surface
> during playback?
> 
> I guess so - but then I don't really know, so don't take
> anything I say as fact.
> 
> I just looked at the results of ffmpeg -i foo.xyz foo.yuy
> and they seem quite variable.
> 
> Nearly all go over/under a bit some quite a lot and they
> include 0 and 255, it does seem like this is what the source
> provides - eg. there are (almost) perfectly behaved streams
> like
> 
> ftp://ftp.tek.com/tv/test/streams/Element/MPEG-Video/625/100b_040.m2v
> 
> Which at least indicates that ffmpeg isn't doing anything
> strange.
> 
> Others in that dir are quite variable even between the 420
> and 422 (*_400.m2v) variants of the same stream.
> 
> I've looked at broadcast mpeg2/dvd and h264 and the results
> usually include out of range values.
> 
> Even a raw reference stream which has never been encoded
> like -
> 
> ftp://vqeg.its.bldrdoc.gov/HDTV/SVT_exports/SVT_Abekas_Exports_/NewMobCal_Abekas_1080i2997_/
> 
> goes over/under (that's assuming it's meant to be tv levels
> - it looks a bit washed out playing full range)
> 
> > If so, I would presume that these out of range values
> are clipped.
> 
> I think that's a decision for display time - and clamped
> rather than clipped.
> 
> > Can ffmpeg do this for me?
> 
> I don't know and I don't know if it would be better to just
> leave alone.
> 
>