[mythtv] HVEC frame counting broken

[John P Poet]

On Sun, Sep 25, 2022 at 8:17 PM Scott Theisen <scott.the.elm at gmail.com>
wrote:

> On 9/25/22 18:48, John P Poet wrote:
>
> On Sun, Sep 25, 2022 at 3:16 PM Scott Theisen <scott.the.elm at gmail.com>
> wrote:
>
>>
>>
>> On 9/25/22 12:42, John P Poet wrote:
>>
>> On Sun, Sep 25, 2022 at 10:40 AM John P Poet <jppoet at gmail.com> wrote:
>>
>>> On Sun, Sep 25, 2022 at 10:33 AM Scott Theisen <scott.the.elm at gmail.com>
>>> wrote:
>>>
>>>> On 9/25/22 11:43, John P Poet wrote:
>>>>
>>>>
>>>>
>>>> Thank you Scott. I just uploaded a HEVC sample to dropbox. It should be
>>>> shared with you.
>>>>
>>>>
>>>> I have the sample.
>>>>
>>>>
>>>> Without 7b2ac1eeb5, HEVCParser::parseSPS detects the
>>>> sps_id: 0
>>>> width, height: 1920x1088
>>>> unitsInTick / timeScale: 166817 / 10000000
>>>>
>>>> With 7b2ac1eeb5, HEVCParser::parseSPS the spd_id, width and height are
>>>> garbage and the unitsinTick / timeScale are never decoded --
>>>> vps_extension_flag is zero.
>>>>
>>>> My best guess is that there is an alignment issue and the BitReader
>>>> that is being passed into HEVCParser::parseSPS is not pointing at the
>>>> correct position.
>>>>
>>>>
>>>> OK, but how are you getting the code to execute on the sample?
>>>> mythcommflag --rebuild something?  Adding to Videos and scanning for
>>>> changes?
>>>>
>>>> Thanks,
>>>>
>>>> Scott
>>>>
>>>
>>> I am using an ExternalRecorder (https://github.com/jpoet/Magewell2TS).
>>> Using the mythfilerecorder ExternalRecorder that is packaged with Myth
>>> should provide the same result. I am pretty sure that `mythcommflag
>>> --rebuild` results in a different code path and I have not tried it.
>>>
>>> If you have trouble setting up mythfilerecorder I will do that this
>>> afternoon and then send you instructions.
>>>
>>
>> Actually, I won't. I keep forgetting that I don't currently have access
>> to my development machine and my production machine will be recording
>> football today. So, that would have to wait until tomorrow sometime.
>>
>> John
>>
>>
>> I couldn't figure out how to get mythfilerecorder to work, so
>> instructions from you, or anyone, would be appreciated.
>>
>> Scott
>>
>
> I cannot test this until tomorrow, but this should work...
>
> Put the attached config files in /home/mythtv/etc/ . Modify
> externfile.conf so it can find the sample hevc file.
>
> Create a new "capture card" of type "External (blackbox) Recorder". For
> the command path use "/usr/local/bin/mythexternrecorder --conf
> /home/mythtv/etc/externfile.conf". Modify that if your mythexternrecorder
> is not in /usr/local/bin.
>
> You may want/need to create a new source for this capture card.
>
> You can do a "channel scan" for the new input and it will pick up the test
> channel defined in channels.conf. You can then create a manual record for
> that channel and it will effectively "record" the hevc sample file.
>
>
>
> Thanks, that worked, adjusting the paths to the real values.  However, it
> loops the input file and creates recordings far longer than the specified
> manual recording duration.
>
> I can confirm that parsing is broken. :(
>
> Let me know if you want me to open a pull request reverting the change to
> BitReader, while I investigate.
>
> Thanks,
>
> Scott
>
> PS--Unrelated, but apparently "HEVC" is not a valid registration
> descriptor according to MythTV:
> ```
> 2022-09-25 20:57:29.612931 D [17701/17792] ExternSH mpegstreamdata.cpp:463
> (CreatePMTSingleProgram) - MPEGStream[8](0x7f2f840261b0): Program Map
> Section
>   PSIP tableID(0x2) length(35) extension(0x1)
>        version(0) current(1) section(0) last_section(0)
>        pnum(1) pid(0x1000) pcrpid(0x100)
>   Stream #0 pid(0x100) type(0x24 video-h265)
>     Registration Descriptor: 'HEVC' Unknown, see
> http://www.smpte-ra.org/mpegreg/mpegreg.html
>   Stream #1 pid(0x101) type(0x81 audio-ac3)
>     Registration Descriptor: 'AC-3' ATSC audio stream A/52
> ```
>

Interesting about the HEVC descriptor. I will look into that. I will also
look into the looping you mention. I will probably wait until I have direct
access to my "dev" machine first, though, since doing that kind of
debugging is inconvenient on a live system.

If you can figure out the problem within the next few of days, then you can
leave it. If you think it will take longer, then yes I would like that
commit to be reversed.

Thank you,

John
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