[FFmpeg-devel] [PATCH] Implement in lavc a flag which makes avcodec_open() to choose the best framerate

[Stefano Sabatini]

On date Thursday 2008-09-11 23:44:18 +0200, Stefano Sabatini encoded:
> On date Thursday 2008-09-11 05:52:01 +0200, Michael Niedermayer encoded:
> > On Sun, Aug 31, 2008 at 08:58:53PM +0200, Stefano Sabatini wrote:
[...]
> > maybe returning an index into the list would be more flexible.
> > Its easy to convert a index to the AVRational not easy though
> > the other way around.
> 
> Yes my only doubt is about the name:
> is av_find_nearest_q_idx OK?
[...]
> Index: libavutil/rational.h
> ===================================================================
> --- libavutil/rational.h	(revision 15295)
> +++ libavutil/rational.h	(working copy)
> @@ -113,4 +113,11 @@
>   */
>  AVRational av_d2q(double d, int max) av_const;
>  
> +/**
> + * Finds the nearest value in \p q_list to \p q.
> + * @param q_list an array of rationals terminated by {0, 0}
> + * @return the index of the nearest value found in the array
> + */
> +int av_find_nearest_q_idx(AVRational q, AVRational* q_list);
> +
>  #endif /* AVUTIL_RATIONAL_H */
> Index: libavutil/rational.c
> ===================================================================
> --- libavutil/rational.c	(revision 15295)
> +++ libavutil/rational.c	(working copy)
> @@ -101,3 +101,49 @@
>  
>      return a;
>  }
> +
> +int av_find_nearest_q_idx(AVRational q, AVRational* q_list)
> +{
> +    int i, nearest_q_idx = 0;
> +    AVRational best_error= (AVRational){INT_MAX, 1};
> +    for(i=0; q_list[i].den; i++) {
> +        AVRational error= av_sub_q(q, q_list[i]);
> +        if(error.num <0) error.num *= -1;
> +        if(av_cmp_q(error, best_error) < 0) {
> +            best_error= error;
> +            nearest_q_idx = i;
> +        }
> +    }
> +    return nearest_q_idx;
> +}
> +
> +#if TEST
> +int main (void) {
> +
> +    AVRational list_q[] = {
> +        {24000, 1001},
> +        {   24,    1},
> +        {   25,    1},
> +        {30000, 1001},
> +        {   30,    1},
> +        {   50,    1},
> +        {60000, 1001},
> +        {   60,    1},
> +        // Xing's 15fps: (9)
> +        {   15,    1},
> +        // libmpeg3's "Unofficial economy rates": (10-13)
> +        {    5,    1},
> +        {   10,    1},
> +        {   12,    1},
> +        {   15,    1},
> +        {    0,    0},
> +    };
> +
> +    AVRational q = { 42, 1};
> +    AVRational nearest_q = list_q[av_find_nearest_q_idx(q, list_q)];
> +#undef printf
> +    printf ("q=%d/%d(%f), nearest_q=%d/%d(%f),\n",
> +            q.num, q.den, (double)q.num/q.den,
> +            nearest_q.num, nearest_q.den, (double)nearest_q.num/nearest_q.den);
> +}
> +#endif /* TEST */
> Index: ffmpeg.c
> ===================================================================
> --- ffmpeg.c	(revision 15295)
> +++ ffmpeg.c	(working copy)
> @@ -208,6 +208,7 @@
>  static int nb_frames_drop = 0;
>  static int input_sync;
>  static uint64_t limit_filesize = 0; //
> +static int force_fps = 0;
>  
>  static int pgmyuv_compatibility_hack=0;
>  static float dts_delta_threshold = 10;
> @@ -3037,23 +3038,10 @@
>  
>          set_context_opts(video_enc, avctx_opts[CODEC_TYPE_VIDEO], AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM);
>  
> +        if (codec && codec->supported_framerates && !force_fps)
> +            fps = codec->supported_framerates[av_find_nearest_q_idx(fps, codec->supported_framerates)];
>          video_enc->time_base.den = fps.num;
>          video_enc->time_base.num = fps.den;
> -        if(codec && codec->supported_framerates){
> -            const AVRational *p= codec->supported_framerates;
> -            const AVRational *best=NULL;
> -            AVRational best_error= (AVRational){INT_MAX, 1};
> -            for(; p->den!=0; p++){
> -                AVRational error= av_sub_q(fps, *p);
> -                if(error.num <0) error.num *= -1;
> -                if(av_cmp_q(error, best_error) < 0){
> -                    best_error= error;
> -                    best= p;
> -                }
> -            }
> -            video_enc->time_base.den= best->num;
> -            video_enc->time_base.num= best->den;
> -        }
>  
>          video_enc->width = frame_width + frame_padright + frame_padleft;
>          video_enc->height = frame_height + frame_padtop + frame_padbottom;
> @@ -3852,6 +3840,7 @@
>      { "vtag", HAS_ARG | OPT_EXPERT | OPT_VIDEO, {(void*)opt_video_tag}, "force video tag/fourcc", "fourcc/tag" },
>      { "newvideo", OPT_VIDEO, {(void*)opt_new_video_stream}, "add a new video stream to the current output stream" },
>      { "qphist", OPT_BOOL | OPT_EXPERT | OPT_VIDEO, { (void *)&qp_hist }, "show QP histogram" },
> +    { "force_fps", OPT_BOOL | OPT_EXPERT | OPT_VIDEO, {(void*)&force_fps}, "force the selected framerate, disable the best supported framerate selection" },
>  
>      /* audio options */
>      { "ab", OPT_FUNC2 | HAS_ARG | OPT_AUDIO, {(void*)opt_bitrate}, "set bitrate (in bits/s)", "bitrate" },

Ping? (As I already wrote I'll remove the test and split the patch
before to commit).

Regards.
-- 
FFmpeg = Frenzy and Fast Mean Programmable Eretic Guide