Reduce Video Frame Rate

This section provides a tutorial example on how to reduce frame display rate of the video stream a SWF file with the '-r nn' option on the output file of the 'ffmpeg' command.

Do you want to try to reduce the frame rate (fps) of a SWF stream file? Here is the "ffmpeg" command to do this:

C:\herong>\local\ffmpeg\bin\ffmpeg 
   -i input.swf -r nn output.swf

"-r nn" specifies the new frame rate for the output file.

Our last sample SWF, Video_and_Audio.swf, has a frame rate of 25. We can reduce it to 12:

C:\herong>\local\ffmpeg\bin\ffmpeg 
   -i Video_and_Audio.swf -r 12 Frame_Rate_Reduced.swf

Input #0, swf, from 'Video_and_Audio.swf':
 Duration: 00:02:03.96, start: 0.000000, bitrate: 127 kb/s
  Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
  Stream #0:1: Video: flv1, yuv420p, 416x240, 25 fps, 25 tbr, 25 tbn

Output #0, swf, to 'Frame_Rate_Reduced.swf':
 Metadata:
  encoder         : Lavf55.40.100
 Stream #0:0: Video: flv1 (flv), yuv420p, 416x240, q=2-31, 200 kb/s, 
              12 fps, 90k tbn, 12 tbc
  Metadata:
   encoder         : Lavc55.63.100 flv
 Stream #0:1: Audio: mp3 (libmp3lame), 44100 Hz, stereo, s16p
  Metadata:
   encoder         : Lavc55.63.100 libmp3lame

Stream mapping:
  Stream #0:1 -> #0:0 (flv -> flv)
  Stream #0:0 -> #0:1 (mp3 -> libmp3lame)

Press [q] to stop, [?] for help
frame=161 fps=0.0 q=13.6 size= 682kB time=00:00:13.41 bitrate=416.4
frame=322 fps=322 q=16.4 size=1252kB time=00:00:26.83 bitrate=382.2
frame=476 fps=319 q=9.8 Lsize=1753kB time=00:00:39.66 bitrate=362.0
   dup=0 drop=510

video:1123kB audio:617kB subtitle:0kB other streams:0kB 
   global headers:0kB muxing overhead: 0.777759%

The output confirms that the new frame rate is 12 fps. And 510 frames where dropped.

Check the output file with "swfdump" command from SWFTools first:

C:\herong>\local\SWFTools\swfdump Frame_Rate_Reduced.swf
[HEADER]   File version: 6
[HEADER]   File size: 1794996
[HEADER]   Frame rate: 12.000000
[HEADER]   Frame count: 476
[HEADER]   Movie width: 416.00
[HEADER]   Movie height: 240.00
[02d]    6 SOUNDSTREAMHEAD2
[03c]   10 DEFINEVIDEOSTREAM defines id 0000 (476 frames, 416x240  ...
[01a]   21 PLACEOBJECT2 places id 0000 at depth 0001 name "video"
[03d] 9058 VIDEOFRAME adds information to id 0000 (frame 0) 416x240...
[013]  421 SOUNDSTREAMBLOCK
[001]    0 SHOWFRAME 1 (00:00:00,000)
[01a]    5 PLACEOBJECT2 moves object at depth 0001
[03d]  896 VIDEOFRAME adds information to id 0000 (frame 1) 416x240...
[013] 1676 SOUNDSTREAMBLOCK
[001]    0 SHOWFRAME 2 (00:00:00,083)
...

The "swfdump" output confirms that the frame rate is reduced to 12 now.

Now enjoy the video with the reduced frame. We don't really feel the video quality is dropped, because our eyes cannot really tell the difference between 12 fps and 25 fps.

C:\herong>\local\bin\flashplayer_13_sa Frame_Rate_Reduced.swf

Try to reduce the frame rate further to 2 fps yourself. You see the impact on the video quality.

Last update: 2014.

Table of Contents

 About This Book

 Introduction of Adobe Flash

 Adobe Flash Player Plugin for Firefox

 Adobe Flash Player Plugin for Chrome

 Adobe Flash Player Plugin for Safari

 Adobe Flash Player ActiveX for IE

 Using "object" Elements for Flash Files

 Using "embed" Elements for Flash Files

 "mp3player" - MP3 Music Player

 SWFObject - Hidding "object" behind JavaScript

 Flash Player Projector

 SWFTools - SWF File Manipulation Tools

 SWFC Script to Generate Flash SWF Files

 ActionScript Embedded in SWFC Script

 AS3Compile - ActionScript 3 Compiler

 Adobe Flex SDK 4

 SWF File Structure and Tags

 SWF File Processing Rules

SWF Files for Video and Audio Streams

 Video and Audio Stream SWF File Structure

 Installing FFmpeg to Manipulate Video SWF Files

 Playing Movie with FFmpeg "ffplay" Command

 See File Properties with FFmpeg "ffprobe" Command

 Convert File Format with "ffmpeg" Command

 Issue with "ffplay" on SWF Output File

 "ffplay" Interactive Commands

 Break Long Video into Parts with "ffmpeg"

 Concatenate Video Files with "ffmpeg"

 Video/Audio Stream Concatenation Order

 Split Audio Stream Out of SWF File

 Split Video Stream Out of SWF File

 Merge Video and Audio Streams to SWF File

 Reduce Video Stream Resolution

Reduce Video Frame Rate

 Outdated Tutorials

 References

 PDF Printing Version