[mythtv-users] Video quality on 0.28 worse than it was on 0.21

[Stephen Worthington]

On Fri, 24 Aug 2018 08:13:11 -0700, you wrote:

>As the subject line suggests, playback is perfect on this exact same
>hardware with 0.21 and is terrible with 0.28.  The video driver is
>different.  Everything else I am able to check is the same.  I can just
>switch the HD without touching anything in the hardware and the playback is
>smooth as silk.  It is almost unwatchable with 0.28.
>
>If it is true that the video driver won't make a difference, then I need to
>go back to 8.04.  I find that difficult to believe.  Perhaps there is some
>other setting, maybe in the backend, I am missing that is different. But
>the playback is terrible even when the backend isn't doing anything except
>sourcing a recording.
>
>The card is a 6200.  I misspoke saying it was a 6600.
>
>Allen

The 6200 and 6600 are similar - no VDPAU.  Cards from back then did do
some sort of support for MPEG acceleration, which I think has been
deleted from mythfrontend as VDPAU is now used to do the same.  So I
would guess that your recordings are using MPEG1 or MPEG2 video
streams, and in 0.21, were using that old acceleration method for
playback.  If your recording sources have never used H.264 video, and
you have not been playing back H.264 video files you have downloaded,
you will not have noticed the lack of support for acceleration of
other video formats, and the 6200 will have been fine.

So if I am right, 0.28 will not support doing the old MPEG
acceleration on a 6200 card - you need to use the 8600GT and get it to
actually use VDPAU in mythfrontend, as your CPU is likely too small to
do the full decoding itself, even for MPEG video files, as witnessed
by your playback problems using the 8600GT without VDPAU.

However, the VDPAU in the 8600GT is only feature set A.  That means
that it does not do the best sort of hardware deinterlacing.  So it
may mean that if you have a lot of interlaced recordings, the video
will not be as smooth with VDPAU on the 8600GT as it was with 0.21
using the old MPEG support on the 6200.  The best deinterlacing
support only became available in VDPAU in the GT220 and above Nvidia
cards with VDPAU feature set C.  That is why I moved to a GT220 card
and pensioned off my old 8600GT - I used it in my Windows box until
its fan died.

You need to find out what is in your recordings to see if they need
deinterlacing and what their video streams are.  The program ffprobe
is normally installed on MythTV systems and can tell you.  This is
what I get from one of my 1080i recordings:

Input #0, mpegts, from '1003_20180824065900.ts':
  Duration: 01:04:57.58, start: 78211.124622, bitrate: 7228 kb/s
  Program 1
    Stream #0:0[0x1c2]: Video: h264 (High) ([27][0][0][0] / 0x001B),
yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 50 tbr, 90k
tbn, 50 tbc
    Stream #0:1[0x190](eng): Audio: aac_latm (HE-AAC) ([17][0][0][0] /
0x0011), 48000 Hz, stereo, fltp
    Stream #0:2[0x19a](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz,
5.1(side), fltp, 384 kb/s
    Stream #0:3[0x3eb]: Unknown: none ([11][0][0][0] / 0x000B)
    Stream #0:4[0x3fc](eng): Subtitle: dvb_subtitle ([6][0][0][0] /
0x0006) (hearing impaired)
    Stream #0:5[0x1f40]: Unknown: none ([5][0][0][0] / 0x0005)
    Stream #0:6[0x3ec]: Unknown: none ([11][0][0][0] / 0x000B)

On the Stream #0 line (the video stream), you can see "h264", "25 fps"
and "50 tbr".  So it is H.264 video, interlaced, 25 frames per second.
If it was not interlaced, it would say "25 tbr".

Or you can install the "mediainfo" program and use it - it gives more
intelligible output.