[Ffmpeg-devel] Re: [theora-dev] FFmpeg Theora encoding patch

[Paul Richards]

In AVCodecContext the time_base gives the time period between frames.
In theora_info they want the frame rate..  These are the inverse of
each other.  :)

I perhaps should have put a little comment there.


On 01/02/07, Eric Dantan Rzewnicki <eric at zhevny.com> wrote:
> On Sat, Jan 06, 2007 at 03:51:28PM +0000, Paul Richards wrote:
> > Hi,
> > ===================================================================
> > +static int encode_init(AVCodecContext* avc_context)
> > +{
> > +    theora_info t_info;
> > +    theora_comment t_comment;
> > +    ogg_packet o_packet;
> > +    unsigned int offset;
> > +    TheoraContext *h = avc_context->priv_data;
> > +
> > +    /** Check pixel format contraints */
> > +    if (check_constraints(avc_context) != 0) {
> > +        return -1;
> > +    }
> > +
> > +    /** Set up the theora_info struct */
> > +    theora_info_init( &t_info );
> > +    t_info.width = avc_context->width;
> > +    t_info.height = avc_context->height;
> > +    t_info.frame_width = avc_context->width;
> > +    t_info.frame_height = avc_context->height;
> > +    t_info.offset_x = 0;
> > +    t_info.offset_y = 0;
> > +    t_info.fps_numerator = avc_context->time_base.den;
> > +    t_info.fps_denominator = avc_context->time_base.num;
>
> This is a naive and probably dumb question ... but why do you flip the
> numerator and denominator here?
>
> > +    if (avc_context->sample_aspect_ratio.num != 0) {
> > +        t_info.aspect_numerator = avc_context->sample_aspect_ratio.num;
> > +        t_info.aspect_denominator = avc_context->sample_aspect_ratio.den;
> > +    } else {
> > +        t_info.aspect_numerator = 1;
> > +        t_info.aspect_denominator = 1;
>
>
> -Eric Rz.
>


-- 
Paul Richards