[mythtv-users] Playback Video Stutters & Audio Quits on one Frontend

[Tim Pletcher]

On Sun, Aug 9, 2020 at 5:47 PM Craig Huff <huffcslists at gmail.com> wrote:

> On Wed, Aug 5, 2020 at 9:05 PM jam <jam at tigger.ws> wrote:
>
>>
>>
>> > On 5 Aug 2020, at 8:09 am, Craig Huff <huffcslists at gmail.com> wrote:
>> >
>> > I'm stumped and need help.  I've been trying to understand why some
>> video files work fine and others give me grief.  If I play a "bad" file on
>> my BE/FE, it plays just fine.  If I play the same file on the remote FE, it
>> will play ok for a second or two, but then the audio quits and the video
>> will stutter like it's in slow motion.  If I play a "good" file, it works
>> just fine anywhere.
>> >
>> > A "bad" file is one of my older recordings that has a file type
>> description of:
>> >           "MPEG sequence, v2, program multiplex"
>> > (using the 'file' command in an xterm).
>> > A "good" file is one of the newer ones with a description of:
>> >           "MPEG transport stream data".
>> >
>> > The BE/FE is based on an ASRock Z77 Extreme4 motherboard with an Intel
>> Core i3-3250 CPU @ 3.50GHz, integrated HD Graphics 2500 and 16GB of RAM.
>> The video connection is DVI-D.
>> >
>> > The remote FE is based on an ASRock A785GM-LE motherboard with an AMD
>> Phenom II X4 965 CPU @3.4GHz, Nvidia GT710 PCI-E 2.0 Graphics adapter, and
>> 4GB of RAM.  The video connection is HDMI (with 5.1 Audio via the HDMI
>> cable).
>> >
>> > The ethernet connection is 1GB/second rated, not tested.
>> >
>> > I fiddled around with various audio options and the pre-defined VDPAU
>> profiles (made things worse! -- audio would drop out faster) vs. the High
>> Quality profile.  I tried tweaking processor settings with cpufrequtils and
>> only managed to get it running so hot it would freeze up until I forced it
>> to shutdown and waited for it to cool off again.
>> >
>> > Short of transcoding the problem files to a format that works, or
>> getting completely new hardware for the remote FE, I'd appreciate any
>> suggestions for what I might have missed to try and get this to work.
>> >
>> > I'd also appreciate any advice on how to transcode the files into a
>> format that will not cause this problem, preferably using Handbrake,
>> Avidemux, and/or ffmpeg.
>>
>> I’d be very interested too!
>> One of my FE is a wireless laptop. Most movies play just fine (including
>> HD), but every now and then is a movie that is always stuttery
>>
>> James
>>
>
> Sadly, rebuilding seek tables didn't change anything.  I believe the
> problem is with SD recordings captured using PVR-500 tuners that I'm trying
> to play back on an HD TV via HDMI on a remote FE.  They play successfully
> on the BE/FE connected to a digital monitor via DVI.  ffprobe describes the
> couple I'm focusing on as:
>         Video: mpeg2video (Main), yuv420p(tv, top first), 720x480 [SAR 8:9
> DAR 4:3], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
>         Audio: mp2, 48000 Hz, stereo, s16p, 384 kb/s
>
> I will try to see what I can come up with to transcode them to MP4 or
> h.264 and see if that helps.  Any suggestions from the peanut gallery
> gratefully appreciated.
>
>
>
Just a guess, but perhaps the presentation timestamps in these older
recordings are messed up.  The audio / video synchronization approach in
v31 was changed to rely on these values from the recording file and perhaps
some decoders are more tolerant than others??

You might look into regenerating timestamps with ffmpeg.  I haven't tried
any of this myself as I don't have old recordings with this issue but some
of the discussion in this thread might provide some options:
https://superuser.com/questions/1159056/ffmpeg-recreate-timestamps-without-reencoding/1358974

Tim
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