[vlc-devel] [Patch] Implementing MP4 DEMUX_GET_FPS control query

[Laurent Aimar]

Hi,

On Fri, Sep 04, 2009, Hugo Beauzee-Luyssen wrote:
> The mp4 demuxer's DEMUX_GET_FPS control query wasn't implemented,
> which was preventing libvlc_media_player_get_fps to access the fps.
> This patch corrects it.

> From 4926a669a00f7bd6639086835655dc7bd3ca22ae Mon Sep 17 00:00:00 2001
> From: Hugo Beauzee-Luyssen <beauze.h at gmail.com>
> Date: Fri, 4 Sep 2009 00:41:36 +0200
> Subject: [PATCH] Implementing MP4 DEMUX_GET_FPS control query
> 
> ---
>  modules/demux/mp4/mp4.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/modules/demux/mp4/mp4.c b/modules/demux/mp4/mp4.c
> index 76aa37c..ebb6023 100644
> --- a/modules/demux/mp4/mp4.c
> +++ b/modules/demux/mp4/mp4.c
> @@ -155,6 +155,7 @@ struct demux_sys_t
>      uint64_t     i_duration;     /* movie duration */
>      unsigned int i_tracks;       /* number of tracks */
>      mp4_track_t  *track;         /* array of track */
> +    float        f_fps;          /* number of frame per seconds */
>  
>      /* */
>      MP4_Box_t    *p_tref_chap;
> @@ -837,8 +838,9 @@ static int Control( demux_t *p_demux, int i_query, va_list args )
>              return VLC_SUCCESS;
>  
>          case DEMUX_GET_FPS:
> -            msg_Warn( p_demux, "DEMUX_GET_FPS unimplemented !!" );
> -            return VLC_EGENERIC;
> +            pf = (double*)va_arg( args, double* );
> +            *pf = (double)p_sys->f_fps;
> +            return VLC_SUCCESS;
>  
>          case DEMUX_GET_META:
>          {
> @@ -1518,6 +1520,8 @@ static int TrackCreateES( demux_t *p_demux, mp4_track_t *p_track,
>              p_track->fmt.video.i_frame_rate_base =
>                  p_box->data.p_stts->i_sample_delta[0];
>          }
> +        p_demux->p_sys->f_fps = (float)p_track->i_timescale /
> +                                (float)p_track->fmt.video.i_frame_rate_base;
 It would be more coherent to use p_track->fmt.video.i_frame_rate instead
of p_track->i_timescale.

 Now, I highly doubt it work well on a lot of files, i_timescale is not bound to
represent the frame rate at all.
 I think the most reliable way would be to count the number of frames and the total
duration to estimate the frame rate. I think that the last message in
TrackCreateSamplesIndex use the needed informations (but I am not sure).

Regards,

-- 
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