[FFmpeg-devel] [PATCH] lavc/rawdec: Only use AV_PIX_FMT_PAL8 for 1 bpp video

Mats Peterson matsp888 at yahoo.com
Sun Jan 31 15:31:05 CET 2016

On 01/31/2016 03:27 PM, Michael Niedermayer wrote:
>> It's not bizarre at all. Black & white is just a variant of
>> palettized data in this context, it's not monochrome. And just
>> because you don't have a non-b/w sample, it doesn't mean you should
>> use monow. A 1 bpp AVI is not monochrome once again, it's
>> palettized, even if it's only with black & white. The same semantics
>> as with 1 bpp depth in QuickTime.
> well, avi is a "old" format and ive worked with avis and maintained
> the avi demuxer for a long time. So if i dont remember a paletted 1bpp
> avi thats some indication that these would be rather rare if they
> exist at all

They are rare, alright, but we should follow the specs, shouldn't we? 
And the specs tell us that 1 bpp AVI is not just black & white but 
palettized, albeit with only 2 colors. TIFF is a different story, it 
explicitly has a "bilevel" format which is black & white only.

>> And since you don't have a "pal2" or "pal4" format, it suddenly
>> seems perfectly OK to convert this to pal8? THere's no logic in
>> this.
> the problem is what happens with the data after the rawvideo decoder
> if its to be stored in a file the encoder will store 8bit paletted data
> (if it supports that) vs. 1bit monochrome data (if it supports that)
> making generated files potentially several times bigger

Not good enough as an argument for using monow. The space increase of 
using pal8 compared to monochrome is hardly an issue nowadays. It was in 
the early 90s, but that was then.


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