[FFmpeg-user] Why are half the frames "duplicate" ?

[DopeLabs]

input: 90k tbn, 59.94 tbc

output: 30k tbn, 29.97 tbc

try explicitly specifying the output frame rate

-c:v h264 -r 29.97


> On Sep 26, 2018, at 7:27 26PM, sean darcy <seandarcy2 at gmail.com> wrote:
> 
> I'm transcoding mpeg2 -> x264.
> 
> Stream #0:0[0x64]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, progressive), 720x480 [SAR 8:9 DAR 4:3], Closed Captions, 29.97 fps, 59.94 tbr, 90k tbn, 59.94 tbc
> 
> When I run ffmpeg:
> 
> ffmpeg -i in.mpg -map 0:0 -map 0:2 -c:v libx264 -tune film -preset slow -crf 22 -c:a copy out.mp4
> 
> almost half the frames are dups:
> 
> frame=394550 fps=135 q=-1.0 Lsize= 2218652kB time=03:39:24.71 bitrate=1380.6kbits/s dup=175142 drop=0 speed=4.51x
> 
> Does this really mean that there were 175,142 frames with exact copies ? So only ( 394,550 less 175,142 ) unique frames ?
> 
> The output looks fine. The input looks fine. What are these duplicated frames? Is it an interlacing issue ? But the input is progressive.
> 
> Does it have to do with this warning:
> 
> [mp4 @ 0x921c80] track 1: codec frame size is not set
> Output #0, mp4, to 'out.mp4':
>  Metadata:
>    encoder         : Lavf58.18.103
>    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 720x480 [SAR 8:9 DAR 4:3], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc
>    Metadata:
>      encoder         : Lavc58.31.100 libx264
> 
> Puzzled.
> 
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