[mythtv] HVEC frame counting broken
John P Poet
jppoet at gmail.com
Mon Sep 26 17:52:26 UTC 2022
On Mon, Sep 26, 2022 at 8:39 AM Scott Theisen <scott.the.elm at gmail.com>
wrote:
> On 9/26/22 08:41, Scott Theisen wrote:
>
> On 9/25/22 21:38, John P Poet wrote:
>
> 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
>
>
> Non byte aligned skip_bits() is broken, try this:
> ```
> diff --git a/mythtv/libs/libmythtv/bitreader.h
> b/mythtv/libs/libmythtv/bitreader.h
> index a40707e08f..dd31b4efdd 100644
> --- a/mythtv/libs/libmythtv/bitreader.h
> +++ b/mythtv/libs/libmythtv/bitreader.h
> @@ -47,14 +47,16 @@ class BitReader
>
> void skip_bits(unsigned n = 1)
> {
> - if (m_cacheSize >= n)
> + if (m_cacheSize > n)
> {
> m_cache <<= n;
> m_cacheSize -= n;
> }
> else
> {
> + n -= m_cacheSize;
> m_cacheSize = 0;
> + m_cache = 0;
> m_bitIndex += n;
> int quotient = m_bitIndex / CHAR_BIT;
> m_bitIndex %= CHAR_BIT;
> ```
>
> It seemed to work for me, but I get `HEVCParser PPS Id 0 not valid yet.
> Skipping parsing of slice.` in the log even with the switch to BitReader
> reverted with your sample.
>
> I thought maybe FFmpeg was doing something to the file, so I switched the
> external recorder command to `command="cat
> /media/data/htpc/hevc-sample.ts"`, but that had no effect.
>
> Regarding looping,
> https://www.mythtv.org/wiki/ExternalRecorder#mythfilerecorder mentions a
> --noloop option for mythfilerecorder, but we aren't using that directly.
>
> I will also make the BitReader unit test more comprehensive before
> creating a pull request with the above fix.
>
> Regards,
>
> Scott
>
>
> See Fix BitReader by ulmus-scott · Pull Request #642 · MythTV/mythtv
> https://github.com/MythTV/mythtv/pull/642 for my fixes and new unit
> tests. Testing would be appreciated.
>
Thanks Scott. I will take a look at it this evening.
John
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