[FFmpeg-devel] [PATCH] lavfi: Port fspp to FFmpeg

[Reimar Döffinger]

On Tue, Dec 23, 2014 at 08:12:50AM +0100, Stefano Sabatini wrote:
> On date Monday 2014-12-22 17:57:34 +0100, Reimar Döffinger encoded:
> > On 22.12.2014, at 17:23, Stefano Sabatini <stefasab at gmail.com> wrote:
> [...]
> > > I'm testing with:
> > > ffmpeg -i matrixbench_mpeg2.mpg -b:v 200k matrixbench_mpeg2-lq.mpg
> > > 
> > > ffplay -f lavfi -i "nullsrc=s=720x576 [bg]; movie=matrixbench_mpeg2-lq.mpg:s=dv+da [v][out1]; [v]split[v1][v2]; [v1]crop=in_w/2:in_h:0:0 [v1pp]; [v2]crop=in_w/2:in_h:in_w/2:0,fspp [v2pp]; [bg][v1pp] overlay[bg+v1pp]; [bg+v1pp][v2pp] overlay=W/2 [out0]"
> > > 
> > > I'm unable to see significant differences in terms of quality between
> > > left and right part of the output (same with mp=fspp, so it doesn't
> > > depend on the port).
> > > 
> > > Is this expected?
> > > 
> > > What's the use case of fspp?
> > 
> > What codec did your lq version end up using? I suspect fspp is most
> > tested and works best with MPEG-4 ASP.  It should significantly
> > reduce blocking - obviously only if your video has significant
> > blocking.  It used to work fairly well on early flv streaming
> > videos.
> 
> Output #0, mpeg, to 'matrixbench_mpeg2-lq.mpg':
>   Metadata:
>     encoder         : Lavf56.16.101
>     Stream #0:0: Video: mpeg1video, yuv420p, 720x576 [SAR 16:15 DAR 4:3], q=2-31, 200 kb/s, 25 fps, 90k tbn, 25 tbc
>     Metadata:
>       encoder         : Lavc56.16.100 mpeg1video
>     Stream #0:1: Audio: mp2, 48000 Hz, stereo, s16, 384 kb/s
>     Metadata:
>       encoder         : Lavc56.16.100 mp2
> Stream mapping:
>   Stream #0:1 -> #0:0 (mpeg2video (native) -> mpeg1video (native))
>   Stream #0:2 -> #0:1 (mp2 (native) -> mp2 (native))

It's possible fspp does not implement (correct) quantizer mapping for
MPEG-1. Plus, MPEG-1 was pretty much irrelevant at the point it was
implemented, so chance are it indeed never worked (at least not in
a useful way) for MPEG-1.