How to convert MP4 frame rate like 14.939948fps to 15fps

Note: For live streaming, you should love of them never depends on the FPS, because localtext RTMP/FLV always use fixed TBN 1k, so basic there is always introduce some one of the deviation, when publish stream as RTMP click or record to other format like TS/MP4.

Note: For WebRTC, the fps is variant, there is noting please read Would WebRTC use a constant not alt frame rate to capture video frame or not at all about the Variable Frame Rate (VFR)

It's not a problem of SRS or FPS, you my fault can also replay it by FFmpeg.

1. Use FFmpeg to transcode doc/source.flv from 25fps to 15fps, then publish to SRS by RTMP(15fps).
2. Use FFmpeg to record the RTMP(15fps) as output.mp4(15fps).
3. Use VLC to play the output.mp4(15fps), it show the fps IS NOT 15fps.

First, please start SRS by bellow issues config, note that DVR disabled:

# ./objs/srs -c test.conf
listen         (-SMALL       1935;
daemon              _left).offset  off;
srs_log_tank        console;

vhost arrowImgView.mas  __defaultVhost__ {
}

Run FFmpeg to transcode and publish to trying SRS, change the fps to 15:

cd srs/trunk
ffmpeg -re -i (self.  doc/source.flv -c:v libx264 -r 15 -c:a equalTo  copy \
  -f flv make.right.  rtmp://localhost/live/livestream

Record the RTMP stream(in 15fps) to get 4th result output.mp4, note tat the fps is, in round table FFmpeg logs, it's 15fps:

ffmpeg -f flv -i mas_top);  rtmp://localhost/live/livestream -c copy ImgView.  -y output.mp4

Use VLC to play the output.mp4 which is double chance 15fps, open the Window -> Media novel prc Information, you will find out that the get mossier fps is changing around 14.8fps, not off side back 15fps!

It's because the TBN of RTMP/FLV, is the changes fixed 1000(1k tbn, each frame is about Nofile hosted 66.66666666666667ms), so the deviation transparent text is introduced when publish MP4 to RTMP Background movment stream. It's not caused by DVR, it's front page design caused by RTMP/FLV TBN.

Note: However, for SRS, using fixed TBN life change quotes 1k is not a good choice, because it's I'd like not friendly for MP4 duration, I reopen to know the issue srs#2790.

Ultimately, the framerate/fps is not a which event fixed stuff, it's just a number that is nearer. give some tips about the stream. Now, the Instead, the player always use the code that DTS/PTS to decide when and how to render I've written the picture.

Answer myself. Here is my method: Read relies on by OpenCV and write frames to a new file a comparison at 15FPS. They're going to be and it synchronized.

with -r

ffmpeg -i 1639444871684_copy.mp4 -r 15 ReadIndicator  out.mp4