[Libav-user] Reading correct frame rate (fps) of input video

[Taha Ansari]

Hi Guohui Huan!

Many thanks for your guidance, I have got it working now!

Thanks once again...


On Wed, May 22, 2013 at 5:58 AM, Guohui Huang <huanggh0108 at sina.com> wrote:

> **
> You can get frame rate as follow:
> AVStream *st = pFormatCtx->streams[your_video_index];
> double frame_rate = st->r_frame_rate.num / (double)st->r_frame_rate.den;
>
> 2013-05-22
>  ------------------------------
>  Guohui Huang
>  ------------------------------
>  *发件人：*Taha Ansari <mtaha.ansari at gmail.com>
> *发送时间：*2013-05-21 23:04
> *主题：*[Libav-user] Reading correct frame rate (fps) of input video
> *收件人：*"This list is about using libavcodec, libavformat, libavutil,
> libavdevice and libavfilter."<libav-user at ffmpeg.org>
> *抄送：*
>
>  Hi!
>
> I am trying to read exact values for frame rate (fps) from any input video
> file. I have been trying to debug different structures like AVFormatCtx,
> etc. but cannot seem to figure it out. For a test case, here is the code I
> have managed (just the source snippet, include files etc. are all
> understandable):
>
>
> //---------------------------------------------------------------------------------------------------------------------------------------------------
>     // ++ test code begins ++//
>     av_register_all();
>     avcodec_register_all();
>     avformat_network_init();
>     avdevice_register_all();
>     AVFormatContext *pFormatCtx = NULL;
>     pFormatCtx = avformat_alloc_context();
>     string finalInputName = "test_input.3gp";
>     avformat_open_input(&pFormatCtx, finalInputName.c_str(), NULL, NULL);
>     if ( pFormatCtx == NULL            ||
>         pFormatCtx->iformat == NULL    )
>     {
>         return -1;
>     }
>     // Retrieve stream information
>     if(avformat_find_stream_info(pFormatCtx, NULL)<0)
>         return -1; // Couldn't find stream information
>
>     // Dump information about file onto standard error
>     av_dump_format(pFormatCtx, 0, finalInputName.c_str(), 0);
>     // -- test code ends --//
>
> //---------------------------------------------------------------------------------------------------------------------------------------------------
>
> The output it gives me is (in debug console):
>
>
> //---------------------------------------------------------------------------------------------------------------------------------------------------
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_input.3gp':
>   Metadata:
>     major_brand     : 3gp4
>     minor_version   : 0
>     compatible_brands: isom3gp4
>     creation_time   : 2013-05-20 11:54:39
>   Duration: 00:00:23.77, start: 0.000000, bitrate: 5882 kb/s
>     Stream #0:0(eng): Video: mpeg4 (Advanced Simple Profile) (mp4v /
> 0x7634706D)
> , yuv420p, 640x480 [SAR 1:1 DAR 4:3], 5752 kb/s, 30.08 fps, 30.08 tbr, 90k
> tbn,
> 300 tbc
>     Metadata:
>       creation_time   : 2013-05-20 11:54:39
>       handler_name    : VideoHandle
>     Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 16000 Hz, stereo,
> s16, 127
>  kb/s
>     Metadata:
>       creation_time   : 2013-05-20 11:54:39
>       handler_name    : SoundHandle
>
> //---------------------------------------------------------------------------------------------------------------------------------------------------
>
> Like in above example, I can read that video is recorded at 30.08 fps,
> question is: it is apparently very simple for FFmpeg to figure this out,
> but how can I use this information from my own program? I was trying to
> follow code from FFmpeg source file (utils.c): [void
> av_dump_format(AVFormatContext *ic,  int index, const char *url, int
> is_output)], but was easily lost there.
>
> Can anyone kindly guide me how to intercept this problem?
>
> Thanks in advance for your time...
>
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>
>
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