[FFmpeg-user] Change the fps of mp4 file during streaming without restarting video

mahek delawala m.delawala95 at gmail.com
Mon Jun 11 17:03:43 EEST 2018

Hi Moritz,

I am having some issues regarding changing the fps of the streamed video.

I am applying the following ffmpeg command on the terminal which has 30 fps
in the output and pushes the stream to wowza server.
ffmpeg -re -i ~/Videos/Movie/Chhello\ Divas\ 2015.mp4 -acodec copy  -r 30
-f rtsp -muxdelay 0.01  rtsp://mahek:Mahek@123@

During the execution of the above command, i am applying the below command
simultaneously in other terminal which has 15 fps in the output.
ffmpeg -re -i ~/Videos/Movie/Chhello\ Divas\ 2015.mp4 -acodec copy  -r 15
-f rtsp -muxdelay 0.01  rtsp://mahek:Mahek@123@

I am able to see that fps gets changed in the second terminal but I am not
able to see the video in vlc in any of the above command ( vlc just plays
the audio stream, video stream is not present).

Following are my queries regarding changing the fps of the streamed video :
1. What can I do so that I am able to see the video track in vlc ?
2. When I am entering the second command it starts from 00:00:00 time, so
how can I check the exact instance of time at which change in fps has
resulted in video ? (for example if I am having 10 min video and I have
entered first command, it starts streaming now after 5 minutes I am
applying second command in another terminal it also starts with 00:00:00
time now. Actually, FPS Changes effect must come from the 5 mintues(the
time at which i executed fps chagne command) only, Video plying must not be
start from the beginning.)

On 11 June 2018 at 00:45, Moritz Barsnick <barsnick at gmx.net> wrote:

> On Sun, Jun 10, 2018 at 23:05:31 +0530, mahek delawala wrote:
> > I am having one mp4 file. During the streaming of the file I want to
> change
> > the fps of video file without restarting the video or without creating
> the
> > new mp4 file with modified fps.
> Assuming you are using ffmpeg for streaming, use "-r <fps>" as an
> output option (i.e. before your output stream URI).
> Note that ffmpeg will achieve this frame rate by dropping or
> duplicating frames. If you want to interpolate, you need to use a
> filter.
> Note also that this doesn't work with the video copy codec (-c:v copy).
> Cheers,
> Moritz
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