[FFmpeg-trac] #1573(undetermined:new): Enhancing -ss option

FFmpeg trac at avcodec.org
Wed Jul 25 12:40:58 CEST 2012

#1573: Enhancing -ss option
             Reporter:  burek        |                     Type:
               Status:  new          |  enhancement
            Component:               |                 Priority:  wish
  undetermined                       |                  Version:
             Keywords:               |  unspecified
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
 Consider the following example command line:
 ffmpeg -ss 00:03:00 -i input -vframes 1 out.jpg
 The result will be 1 image frame somewhere around 3rd minute, depending on
 gop size of the input, at the last found keyframe, but the seeking will be
 extremely fast.

 Now consider this line:
 ffmpeg -ss 00:02:30 -i input -ss 00:00:30 -vframes 1 out.jpg
 The output will be the exact image frame at the 3rd minute of the input
 and the seeking will be very fast for the first 2 and a half minutes,
 following the slow seeking (frame-by-frame) for the next 30 seconds,
 resulting in the combination of the fast and accurate seeking.

 My question is if the -ss input option (before -i) can be enhanced in such
 a way that it automatically adds another -ss output option (after -i)
 which will compensate for the difference between the last found keyframe
 and the user specified seek time.

 For example, if the last found keyframe in that input was at 00:02:57, the
 result should be the same as if the user has typed:
 ffmpeg -ss 00:02:57 -i input -ss 00:00:03 -vframes 1 out.jpg

 I hope you get my point. The idea is to seek as fast as possible until the
 last keyframe in the specified interval and then to slowly seek to the
 precise time point, specified by user, all automatically, without users
 having to investigate the input to find out the last keyframe's position.

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1573>
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