Opened 11 months ago

Last modified 3 months ago

#13292 assigned Bug Report - General

LiveTV Channel Switching - DVB-T/T2 UK Freeview

Reported by: Mike Bibbings Owned by: Peter Bennett
Priority: minor Milestone: needs_triage
Component: MythTV - DVB Version: Master Head
Severity: medium Keywords:
Cc: Ticket locked: no

Description

I am seeing a number of issues in LiveTV when changing to certain channels on DVB-T/T2 UK Freeview. The symptoms vary from an ok channel change, to video with no audio, vidio with wrong audio (subtitle fails) to "cannot open decoder".

It seems that codec detection for LiveTV is having problems with certain channels, where mp3 codec is detected. It is particularly noticeable for Sky News channel.

The issues are also present on mythtv 29, so the recent bump to ffmpeg 4 in master does not seem to be the cause.

mythtv 0.28 works but also has the Ring Buffer detection issues, but channel change is ok.

Note Channel switching times are also long due to Ring Buffer detection not failing, it falls back to in-file.

Attached are a number of debug logs including ffmpeg, mythffmpeg and mediainfo data taken from a recording of Sky News channel.

Attachments (11)

mythfrontend.20180605105537.8267-skynews-ok-tuning-with-audio.log (149.6 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180605180723.4343-skynews-noaudio.log (349.1 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180605181230.4437-skynews-could-not-open-decoder.log (126.7 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180605181924.4793-recorded-skynews-playback.log (110.7 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180606054416.6887-mythtv-028-xubuntu1604.log (658.6 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180606061614.2257-mythtv29-debian-stretch.log (244.9 KB) - added by Mike Bibbings 11 months ago.
skynews-ts-data.txt (9.2 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180605175952.4153-yourtv.log (122.9 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180608062200.29257-ITVHD.log.zip (151.5 KB) - added by Mike Bibbings 11 months ago.
mythfrontend.20180615130657.23054-various-channel-switch-withdebug-patch.log (669.1 KB) - added by Mike Bibbings 10 months ago.
disable_avformatdecoder_return_FAIL_DEBUGONLY.patch (613 bytes) - added by Mike Bibbings 10 months ago.

Change History (20)

Changed 11 months ago by Mike Bibbings

Changed 11 months ago by Mike Bibbings

Changed 11 months ago by Mike Bibbings

Changed 11 months ago by Mike Bibbings

Changed 11 months ago by Mike Bibbings

Changed 11 months ago by Mike Bibbings

Changed 11 months ago by Mike Bibbings

Attachment: skynews-ts-data.txt added

comment:1 Changed 11 months ago by Mike Bibbings

Channel your tv log shows difference with no mp3 codec detected, with Ring Buffer detection working and quick channel change.

Changed 11 months ago by Mike Bibbings

comment:2 Changed 11 months ago by Mike Bibbings

Correction to first post: "Ring Buffer detection not failing" should be "Ring Buffer detection failing"

comment:3 Changed 11 months ago by Mike Bibbings

transport dumps for skynews, single channel and full mux are available at https://www.dropbox.com/sh/0n0t3ebp4nwiy3g/AACeC4WijoHLzj6Mrq1pgdmDa?dl=0

comment:4 Changed 11 months ago by bib1963

Sorry, can't help you other than confirm the problem, although if you up the card signal & tuning timeouts, that does seem to help. I've set mine to 10,000ms

comment:5 in reply to:  4 Changed 11 months ago by Mike Bibbings

Replying to bib1963:

Sorry, can't help you other than confirm the problem, although if you up the card signal & tuning timeouts, that does seem to help. I've set mine to 10,000ms

Yes, increasing timeouts does help (I had already done this), but they only mask the problem.

comment:6 Changed 11 months ago by Mike Bibbings

Added another mythfrontend.20180608062200.29257-ITVHD.log, this shows issues with DVB-T2 HD channel.

Changed 11 months ago by Mike Bibbings

comment:7 Changed 11 months ago by Mike Bibbings

I have added 8 full ts dump files (all multiplexes from SandyHeath? Freeview Transmitter) to my dropbox https://www.dropbox.com/sh/0n0t3ebp4nwiy3g/AACeC4WijoHLzj6Mrq1pgdmDa?dl=0

The files are c<nn>-fullts.ts and are 30 second dumps using dvbv5-zap

Mike

comment:8 Changed 10 months ago by Mike Bibbings

Done some more investigations, the issue seems to be (mainly) with audio stream detection.

I applied a patch which disabled FAIL return in avformatdecoder.cpp (attached disable_avformatdecoder_return_FAIL_DEBUGONLY.patch)

The attached log mythfrontend.20180615130657.23054-various-channel-switch-withdebug-patch.log

shows a number of entries like:

2018-06-15 14:07:44.328931 D [23054/23054] CoreContext? avformatdecoder.cpp:205 (has_codec_parameters) - AFD: unspecified frame size

With the patch applied channel tuning is far faster, as audio seems to sort itself out, and detection now works in RingBuffer? (it no longer drops back to in-file).

Changed 10 months ago by Mike Bibbings

Changed 10 months ago by Mike Bibbings

comment:9 Changed 3 months ago by Peter Bennett

Owner: set to Peter Bennett
Status: newassigned
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