[mythtv-users] HD-PVR bitrate not being set in v29? [SOLVED]

Dan Wilga mythtv-users2 at dwilga-linux1.amherst.edu
Fri Nov 2 18:33:52 UTC 2018


On 10/8/18 9:11 AM, Dan Wilga wrote:
> On 10/5/18 4:11 PM, john wrote:
>> On 2018-10-04 9:49 a.m., mythtv-users2 at dwilga-linux1.amherst.edu 
>> (Dan Wilga) wrote:
>>> I recently noticed that my free disk space was creeping downward, and
>>> decided to investigate. I discovered that many recordings made since I
>>> switched from 0.28.2 to 29.1 are consistently larger--sometimes double
>>> or triple in size.
>>>
>>> Looking further, I noticed that the bitrate of the HD-PVR (not HD-PVR2)
>>> recordings seems to be much higher than it should be. SoI checked the
>>> recording profiles in mythtv-setup. I have confirmed that the 
>>> recordings
>>> rules in question are using my Low Quality profile, which has this for
>>> all three (low, med, high) resolutions:
>>>
>>> Avg. Bitrate: 4500 Max. Bitrate: 6200
>>>
>>> What is clear is that recordingsdon't seem to be using this value.
>>> Taking the output of mediainfo from a 0.28.1 recording and comparing it
>>> to that of a 29.1 recording of the same program on another night gives
>>> this diff:
>>>
>>> # diff /tmp/1 /tmp/2
>>> 5,6c5,6
>>> < File size : 835 MiB
>>> < Duration : 33 min 25 s
>>> ---
>>>   > File size : 2.52 GiB
>>>   > Duration : 33 min 24 s
>>> 8c8
>>> < Overall bit rate???????????????????????? : 3 490 kb/s
>>> ---
>>>   > Overall bit rate???????????????????????? : 10.8 Mb/s
>>> 21c21
>>> < Duration : 33 min 25 s
>>> ---
>>>   > Duration : 33 min 23 s
>>> 23c23
>>> < Bit rate : 2 929 kb/s
>>> ---
>>>   > Bit rate : 9 891 kb/s
>>> 35,36c35,36
>>> < Bits/(Pixel*Frame) : 0.047
>>> < Stream size : 700 MiB (84%)
>>> ---
>>>   > Bits/(Pixel*Frame) : 0.159
>>>   > Stream size : 2.31 GiB (91%)
>>> 48c48
>>> < Duration : 33 min 26 s
>>> ---
>>>   > Duration : 33 min 24 s
>>> 58c58
>>> < Stream size : 91.8 MiB (11%)
>>> ---
>>>   > Stream size : 91.8 MiB (4%)
>>>
>>> At the same time, while a recording is ongoing, the output of "v4l2-ctl
>>> -l" gives these values:
>>>
>>> video_encoding (menu)?? : min=0 max=2 default=2 value=2
>>> video_bitrate_mode (menu)?? : min=0 max=1 default=1 value=0 
>>> flags=update
>>> video_bitrate (int)??? : min=1000000 max=13500000 step=100000
>>> default=6500000 value=13500000
>>> video_peak_bitrate (int)??? : min=1100000 max=20200000 step=100000
>>> default=9000000 value=20200000
>>>
>>> The recording bitrates are maxed. It's as though the values in the
>>> profile aren't being used, even though they are in the range of
>>> acceptable values (once you multiply by 1000). Can Anyone else with an
>>> HD-PVR confirm this?
>>>
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>>>
>> I'm seeing the same thing on 29. Opened a bug report (13317) with 
>> more information a little while ago, but don't know if anyone's 
>> looking at it or whether this also occurs in 30/testing.
>>
>> It happens to me with my HD-PVR recordings immediately on upgrade 
>> from .28 to 29-fixes (using Mythbuntu PPA). Bitrate settings from 
>> Recording Profiles in Mythtv-Setup are applied just fine to 
>> recordings in .28, but on upgrade to 29 they are ignored, and some 
>> sort of what-looks-like generic settings are applied to all HD-PVR 
>> recordings instead: 720p records with VBR at 9000/13500 kbps, 
>> regardless of settings in Mythtv-Setup being set to 13500 average 
>> bitrate and 6500 for max bitrate which should, I believe, result in 
>> CBR at 13500.
>>
>> I verified by checking the recordings from .28 and 29fixes both with 
>> mediainfo, and also by checking in-progress recordings by running the 
>> v4l2-ctl command to display bitrate info (sorry at work and don't 
>> remember exact command).
>>
>> As you would expect, I also see smaller file sizes and a decrease in 
>> video quality with the lower bitrate recordings on 29, despite the 
>> fact that the Recording Profile settings for the HD-PVR are unchanged.
>>
>> I tried swapping in a new hdpvr power supply and a replacement hdpvr 
>> board to eliminate hardware issues but got the same results. Tried it 
>> out on a test machine with a fresh install to eliminate corrupted 
>> database possibility, got same results: bitrate settings work in 28 
>> but are no longer applied once I upgrade to 29.
> Over the weekend I enabled extra logging (-v record:info) on my 
> backend. In my case, I can see "Checking Resolution" and "Got 
> Resolution" log messages when it enters 
> MpegRecorder::HandleResolutionChanges, but it doesn't alter the 
> bitrate. It thinks the rate is already correct.
>
> I think I need to add some more logging, to see what values are 
> present when it first enters this method. This will take some time, as 
> I don't want to adversely affect WAF.
A follow-up for anyone following this thread:  Jonatan Lindblad 
suggested a patch, both John and I tested it, and it has now been 
committed to fixes/29 (987159173d) and master (658dd95fd0).

It turns out that this bug would have likely affected several different 
kinds of tuner, not just the HD-PVR.


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