[FFmpeg-user] Scaling up is pixelated

Moritz Barsnick barsnick at gmx.net
Wed Feb 12 21:49:48 CET 2014


On Wed, Feb 12, 2014 at 07:22:39 -0800, Grant wrote:

> ffmpeg -i sample1.mp4 -filter:v scale=1360:-1 -sws_flags lanczos -c:a
> copy sample2.mp4

You're recoding to larger dimensions with a less efficient codec
(implicit) with a smaller bitrate (observed). That should explain the
drop in quality.

Try explicitly increasing the quality of the output, e.g. by specifying
"-q:v 2". YMMV.

(I must admit I don't know what the "quality" defaults to when encoding
the way you did. It must be documented somewhere. From experience, it's


>     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 720x304 [SAR 1:1 DAR 45:19], 1572 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
>     Stream #0:0(und): Video: mpeg4 ( [0][0][0] / 0x0020), yuv420p, 1360x574 [SAR 1:1 DAR 680:287], q=2-31, 200 kb/s, SAR 2583:2584 DAR 45:19, 24k tbn, 23.98 tbc (default)

More information about the ffmpeg-user mailing list