Transcoding anamorphic videos lowers the resolution unnecessarily

General Discussions
1

A few months ago I started using Plex DVR. Unfortunately there are no unencrypted HD channels around here, so everything I record has a resolution of 720x576. The recordings are still quite OK, but of course I’d like to make sure that I don’t lose any more quality than necessary.

Almost all recordings are 16:9, so the pixels are far from square. If you just scale them up to the correct width, you get 1024x576 with all of the information retained. But I just noticed (thanks to PlexPy showing the resolution of a transcoded video) that Plex instead lowers the resolution of a video when transcoding. That is, the picture shrinks to 720x404. I’ve verified this by using mediainfo to check the media-xxxxx.ts files that Plex generates during transcoding:

...
Duration                                 : 3 min 31 s
Width                                    : 720 pixels
Height                                   : 404 pixels
Display aspect ratio                     : 16:9
...

This of course loses a lot of picture information and sharpness. The culprit seems to be this part of the transcoder parameters, ensuring that the transcoder generates square pixels within a bounding box of 720x576:

-filter_complex [0:0]scale=w=min(720\,iw):h=min(576\,ih):force_original_aspect_ratio=decrease,...

I don’t think re-encoding and storing every recording at a higher resolution of 1024x576 is the solution. Is there anything else I can do to retain the full resolution? Have I misconfigured something? Could Plex transcode to 1024x576, or even better, transcode at the same 720x576 resolution and let the display device scale to the display resolution in a single step?

2

And of course I found a couple of threads discussing exactly the same thing right after I posted it. I did search for the topic earlier but apparently I didn’t use the right search terms…

2014: https://forums.plex.tv/discussion/130104/stop-pms-transcoding-anamorphic-mkv-files-dvd-rips-from-720x576-to-719x404

2016: https://forums.plex.tv/discussion/224666/transcoding-of-anamorphic-video-reduces-resolution

But those threads don’t really resolve the issue, so the questions remain.

3

No solutions?

Going from 720x576 to 718x404 means going from 414720 to 297252 pixels. Only 71.7% of the pixels are left, which is kind of noticeable when the resolution isn’t that high to begin with.

4

This seems to be fixed now:

Width                                    : 1 024 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 16:9