[FFmpeg-devel] WORDS_BIGENDIAN used in installed header avutil.h

Baptiste Coudurier baptiste.coudurier
Fri Jan 30 11:40:05 CET 2009

Michael Niedermayer wrote:
> On Thu, Jan 29, 2009 at 04:24:22PM -0800, Baptiste Coudurier wrote:
>> Michael Niedermayer wrote:
>>> On Thu, Jan 29, 2009 at 03:20:10PM -0800, Baptiste Coudurier
>>> wrote:
>>>> Michael Niedermayer wrote:
>>>>> On Thu, Jan 29, 2009 at 02:36:53PM -0800, Baptiste Coudurier
>>>>> wrote: [...]
>>>>>>>> considering both values since the goal is to deprecate
>>>>>>>> all _1 (horrible names)
>>>>>>> You are free to suggest better names for the _1 cases, we
>>>>>>> can surely rename them in the next major bump
>>>>>> The best names are RGBA8888, BGRA8888, ARGB8888, ABGR8888,
>>>>>> IMHO. Now RGBA, BGRA, ARGB, ABGR are ok too.
>>>>>> And this is what should be as external API, there is _no_
>>>>>> sense if hacking pixfmt externally.
>>>>>> If libswscale wants to optimize routines based on its
>>>>>> internal implementation (using uint64_t or uint32_t) to
>>>>>> deal with data, it's _its_ problem, not users which should
>>>>>> see what is _obvious_.
>>>>> i dont mind if we move the byte based RGBA, ... into the enum
>>>>> and move the RGB32 stuff to the #defines with the next major
>>>>> bump (it would break ABI not API) assuming someone posts a
>>>>> patch ...
>>>>> iam not in favor of droping the native 32bit word formats nor
>>>>> do i agree that this is just sws problem, it really is not. a
>>>>> grep in mplayer confirms this also, the 32bit word formats
>>>>> are used the byte based formats are not.
>>>> Well, mplayer is one thing, I know that several people already
>>>> asked how to access raw data from AVFrame.
>>> these people will keep asking no matter what you do with the
>>> pixel formats you arent expecting them to grok the stuff you
>>> wrote about rgb15/16 below do you?
>> At least it is obvious to me. IMHO it is more obvious than groking
>> arch dependant description.
>> We all know people are not careful about arch dependant code and 
>> concepts. I care about usually and simplicity.
>>> The current stuff is well explained in the header so unless
>>> someone fails to find that he shouldnt have a problem, if he does
>>> fail to find it so will he if something else is writen i there
>> Last time I tried to add support for RGBA32 of whatever variant 
>> quicktime use, I was so confused about these arch dependant things
>> and these arch dependant defines that I gave up.
>> I hated the guy who decided that buf[0] for RGBA what not 'R' for 
>> whatever reason.
> now we have a problem because buf[0] of PIX_FMT_RGBA is R could you
> elaborate on what did not work?

I was trying to figure out what pixfmt to use, according to what my
buffer contained, according to specs, then I was confused by RGB32_1 or
RGBA or whatever, however I knew for sure that buf[0] was R, buf[1] was
G, buf[2] was B, and buf[3] was A.

>>>> If you don't want to use libswscale because it's GPL for
>>>> example or you want to write your own conversion routine or
>>>> filter, it is definitely more simple and obvious to have arch
>>>> independant representation in uint8_t buffer.
>>> Iam not aware of anyone who tried to access rgb15/16 as bytes in
>>> a serious application and succeeded. swscale, the old scaler as
>>> well as mplayer use 16bit scalers or SIMD
>> I did try to mess with RGB555 in .mov, and I gave up both in
>> libswscale and imgconvert because of the arch dependant mess in
>> pixfmt.
>> We don't agree here.
> [...]
>> Well, I only see 4 needed pixfmt: RGB1555, RGB5551, BGR5551,
>> BGR1555.
> [...]
>> Well, IMHO this is easy, RGB5551: rrrrrgggggbbbbb1 |   0    |   1
>> |
> the 8 variants, and maybe one is what mov uses (and iam of course not
> claiming all are used in practice but they could)
> RGB5551: rrrrrggg ggbbbbb1 |   0    |   1    |
> RGB1555: 1rrrrrgg gggbbbbb |   0    |   1    |
> BGR1555: 1bbbbbgg gggrrrrr |   0    |   1    |
> BGR5551: bbbbbggg ggrrrrr1 |   0    |   1    |
> RGB5551X ggbbbbb1 rrrrrggg |   0    |   1    |
> RGB1555X gggbbbbb 1rrrrrgg |   0    |   1    |
> BGR1555X gggrrrrr 1bbbbbgg |   0    |   1    |
> BGR5551X ggrrrrr1 bbbbbggg |   0    |   1    |
> and before you say the X varints dont exist RGB1555X/BGR1555X are the
> only of the 8 i remember seeing, they are what your *vga card uses on
> x86 iam not sure of the 5551 variants exist

Sorry, I don't understand here how you get the X variants, why would
someone pack values this way, considering you have 3 separate values at
the beginning, also btw, I don't know much about vga card, nor rgb555

I'm confused anyway, why aren't these 8 variants in avutil.h ?

Also I grep for BGR32 in libavcodec, there is no match. Why is this
pixfmt defined ?

What is obvious however is that their name is clearly misleading
considering what you would have in your uint8_t *buffer.

Anyway, you still have to find a way to get WORDS_BIGENDIAN defined
somewhere, this is _critical_ like Diego pointed.


Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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FFmpeg maintainer                                  http://www.ffmpeg.org

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