[FFmpeg-devel] [RFC/PATCH 6/8] tidsp: add mp4v configuration

[Felipe Contreras]

On Tue, Sep 7, 2010 at 10:54 PM, Reimar D?ffinger
<Reimar.Doeffinger at gmx.de> wrote:
> On Tue, Sep 07, 2010 at 10:26:05PM +0300, Felipe Contreras wrote:
>> On Tue, Sep 7, 2010 at 10:15 PM, Reimar D?ffinger
>> <Reimar.Doeffinger at gmx.de> wrote:
>> > On Tue, Sep 07, 2010 at 12:44:12PM +0300, Felipe Contreras wrote:
>> >> On Tue, Sep 7, 2010 at 5:45 AM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>> >> > On Sun, Sep 5, 2010 at 6:15 PM, Felipe Contreras
>> >> > <felipe.contreras at gmail.com> wrote:
>> >> >> +struct mp4vdec_args {
>> >> >> + ? ? ? uint32_t size;
>> >> >> + ? ? ? uint16_t num_streams;
>> >> >> +
>> >> >> + ? ? ? uint16_t in_id;
>> >> >> + ? ? ? uint16_t in_type;
>> >> >> + ? ? ? uint16_t in_count;
>> >> >> +
>> >> >> + ? ? ? uint16_t out_id;
>> >> >> + ? ? ? uint16_t out_type;
>> >> >> + ? ? ? uint16_t out_count;
>> >> >> +
>> >> >> + ? ? ? uint16_t reserved;
>> >> >> +
>> >> >> + ? ? ? uint32_t max_width;
>> >> >> + ? ? ? uint32_t max_height;
>> >> >> + ? ? ? uint32_t color_format;
>> >> >> + ? ? ? uint32_t max_framerate;
>> >> >> + ? ? ? uint32_t max_bitrate;
>> >> >> + ? ? ? uint32_t endianness;
>> >> >> + ? ? ? uint32_t profile;
>> >> >> + ? ? ? int32_t max_level;
>> >> >> + ? ? ? uint32_t mode;
>> >> >> + ? ? ? int32_t preroll;
>> >> >> + ? ? ? uint32_t display_width;
>> >> >> +};
>> >> >
>> >> > What are all these?
>> >>
>> >> These are arguments needed to start the DSP algorithm.
>> >
>> > Assuming you mean they are directly pass to hardware:
>> > I don't think a struct is a good way to do this,
>> > you're relying on the compiler not inserting some
>> > padding just because it likes to (e.g. on a machine
>> > that can only do 32 bit read and writes it might allocate
>> > 4 bytes for all the uint16_t - I admit I haven't double-
>> > checked this is indeed allowed).
>>
>> You mean padding at the end, or in the middle? Appending stuff at the
>> end is generally not a problem (although some algos check the size
>> specified). If it's in the middle... how do you suggest fixing that?
>
> Building the memory layout manually using bytestream_put_...(),
> using comments to describe what's written where (since there's
> no more variable names to guess it from anymore).

But the code in the 'tidsp' apparently wouldn't belong to FFmpeg, so
the bytestream_* utilities are not available.

-- 
Felipe Contreras