[mythtv-users] mythtv v30 'Could not open decoder' error

Tim Pletcher pletchtd at gmail.com
Thu Jan 31 20:47:01 UTC 2019

On Thu, Jan 31, 2019 at 12:47 PM Mike Bibbings <mike.bibbings at gmail.com>

> On 31/01/2019 14:47, Tim Pletcher wrote:
> On Tue, Jan 29, 2019 at 2:11 PM Tim Pletcher <pletchtd at gmail.com> wrote:
>> On Tue, Jan 29, 2019 at 10:28 AM John <jksjdevelop at gmail.com> wrote:
>>> I also get this error on a remote frontend with version 30. Some timeout
>>> must need a tweak. Note the issue has been there for several weeks it is
>>> not due to a very recent change. I don't use live tv enough to make it a
>>> major issue for me.
>> Good to know that the problem is not unique to me.  I only updated to v30
>> on Sunday the day prior so it is likely that I simply didn't stumble upon
>> it in the limited use of the system since then.
>> According to this in the log:
>> Jan 28 19:28:13 k-mint mythfrontend.real: mythfrontend[1273]: I CoreContext avformatdecoder.cpp:2772 (OpenAVCodec) AFD: Opened codec 0x55a532b95180, id(AC3) type(Audio)
>> Jan 28 19:28:13 k-mint mythfrontend.real: mythfrontend[1273]: E CoreContext avformatdecoder.cpp:2635 (ScanStreams) AFD: Unknown video codec - defaulting to MPEG2
>> It appears that this is related to fallback to software based decoding rather than GPU Hardware based decoding.  Since this is occurring intermittently, you are probably right that it is a timing issue.
>> Looking at avformatdecoder.cpp and totally speculating because i have no experience with C++, I wonder if is related to SEQ_PKT_ERR_MAX 10 (line 108) which is a criterion used to apply logic to fall back to software decoding?  Is 10 packets perhaps sometimes too sensitive when changing channels via LiveTV?
>> I pulled down the source, increased the SEQ_PKT_ERR_MAX value to 15 in
> avformatdecoder.cpp, and recompiled the frontend.  Since doing that, I have
> not experienced the 'Could not open decoder' error for the last three days
> now when using LiveTV.  I have not noticed any other deleterious effects
> though I will continue to monitor for any.
> On a separate topic, when I recompile the frontend from source, the
> mythfrontend binary I generate is an order of magnitude larger than the one
> in the mythbuntu repo and I can't seem to figure out why.  Looking and
> comparing the ./configure options from the mythbuntu build package with the
> ones I am using, the only tangible difference i see is that my system is
> using NASM rather than YASM for the compilation.  Can anyone educate me on
> what is causing this difference?
> -Tim
> Tim,
> I tried your change to  SEQ_PKT_ERR_MAX on current mythtv master and it
> did not resolve the problem. I also tried other values of 50 and 1000,
> again no resolution.
> For reference my system is Xubuntu 18.04 with Hauppauge QuadHD DVB-T/T2
> using current Hauppauge kernel from the ppa.
> My workround is attached, it disables error checking in
> avformatdecoder.cpp, and only affects LiveTV.
> Mike
> Thank you for passing along your patch Mike.

While we have both observed the same error, I suspect the underlying root
cause may be different in our two cases.  I have not experienced this
'Could no open decoder' error in the prior 6 months on v29 and it first
occurred when I updated to the newly released v30 on last Sunday.

I do experience some similar issues to what you describe in your linked
issue report earlier in the thread. If I try to transition to a program on
another physical tuner via the program guide while watching LiveTV, I will
frequently get a frozen display with audio from the new channel playing in
the background.  If I then retune the same channel again, it will work the
second time.

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