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

[Hugo Beauzee-Luyssen]

On Tue, Sep 8, 2009 at 1:17 PM, Hugo Beauzee-Luyssen <beauze.h at gmail.com> wrote:
> On Sat, Sep 5, 2009 at 11:33 PM, Hugo Beauzee-Luyssen<beauze.h at gmail.com> wrote:
>> On Sat, Sep 5, 2009 at 11:08 AM, Laurent Aimar<fenrir at via.ecp.fr> wrote:
>>> 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,
>>>
>>

Since this is how FPS are computed in this demux, I can't see any
other way of doing this.
Any hints ??

Regards,


-- 
Hugo Beauzée-Luyssen