[FFmpeg-user] Re-encode mpeg2 for same quality

[petesea at frontier.com]

I've had some success solving my mpeg2 bitrate/size issue.  But not really 
sure if the results are valid... or appropriate.

As previously mentioned using -q 1 helps a little but not much.  -mbd 2 
maybe helps a little, not much.  -target doesn't help at all.

The only real success I've had is if I use -minrate and -maxrate with 
different values (see full output below):

   $ ffmpeg -hide_banner -i video.vob -codec:v mpeg2video -b:v 6000k -bufsize 6000k -minrate 4000k -maxrate 9800k -codec:a copy -copyts -f vob video-MINMAX.vob

but then I see the following warning:

   [mpeg2video @ 0x8801520] Warning min_rate > 0 but min_rate != max_rate isn't recommended!

Why is this not recommended?  And what is the consequences of using it?

With regards to the DVR (FFWD/REW) issues, I found that if I use 
HandBrakeCLI to create a mkv/mpeg2 file, then use ffmpeg to convert that 
to mpeg2/mpeg2 (via -c copy) it works fine on my DVR.  Unfortunately, 
HandBrake has the same bitrate/file size issue.  And using "--encopts 
minrate=4000k" with HandBrake doesn't help... it gives the same "not 
recommended" warning, but doesn't increase the overall bitrate.

Nothing I've tried so far using only ffmpeg prevents the FFWD/REW issues.

What could HandBrake be doing different from ffmpeg?   I believe HandBrake 
is actually using ffmpeg for the mpeg2 encoding... although it's own 
version (much older I think).

What possible things might cause this FFWD/REV issue?  bitrate, fps, 
b-frames, I'm just throwing out terms here, because I don't really know.

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$ ffmpeg -hide_banner -i video.vob -codec:v mpeg2video -b:v 6000k -bufsize 6000k -minrate 4000k -maxrate 9800k -codec:a copy -copyts -f vob video-MINMAX.vob
Input #0, mpeg, from 'video.vob':
   Duration: 00:00:14.98, start: 0.513067, bitrate: 4685 kb/s
     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 720x480 [SAR 32:27 DAR 16:9], max. 9800 kb/s, 29.97 fps, 59.94 tbr, 90k tbn, 59.94 tbc
     Stream #0:1[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
[mpeg2video @ 0x8801520] Warning min_rate > 0 but min_rate != max_rate isn't recommended!
Output #0, vob, to 'video-MINMAX.vob':
   Metadata:
     encoder         : Lavf56.15.102
     Stream #0:0: Video: mpeg2video, yuv420p, 720x480 [SAR 32:27 DAR 16:9], q=2-31, 6000 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
     Metadata:
       encoder         : Lavc56.13.100 mpeg2video
     Stream #0:1: Audio: ac3, 48000 Hz, 5.1(side), 448 kb/s
Stream mapping:
   Stream #0:0 -> #0:0 (mpeg2video (native) -> mpeg2video (native))
   Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=  443 fps=102 q=2.0 Lsize=    8364kB time=00:00:15.48 bitrate=4423.6kbits/s dup=88 drop=0
video:7436kB audio:819kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.324703%

$ ffmpeg -hide_banner -i video-MINMAX.vob
Input #0, mpeg, from 'video-MINMAX.vob':
   Duration: 00:00:15.00, start: 0.513067, bitrate: 4567 kb/s
     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 720x480 [SAR 32:27 DAR 16:9], max. 9800 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
     Stream #0:1[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
At least one output file must be specified