[mythtv-users] Patches that improve mythcommflag accuracy

faginbagin mythtv at hbuus.com
Wed Oct 29 06:20:52 UTC 2014


On 10/28/2014 9:37 AM, Carl Hunter wrote:
> On 10/28/2014 12:09 AM, faginbagin wrote:
>> Hi Carl, I did not test recordings made using a PVR-150, but I can.
>> All the recordings I tested were recorded using an hdhomerun. I
>> think my sister still has quite a few old recordings from a
>> PVR-150. These would have been made on 0.23. I've also got a couple
>> of HVR-1600 tuners which have both analog and digital tuners. The
>> analog side of the HVR-1600 uses the same kernel driver, ivtv, as
>> the PVR-150, and as far as mythtv is concerned, they look the same.
>> I haven't used the analog side in a couple of years, but I might
>> try configuring one. I'll get back to you on what I learn. Just to
>> confirm what I think should be obvious: the recording that
>> mythcommflag can't handle is one you can play back without any
>> problem in mythfrontend, right? Can you tell me how you've
>> configured your PVR-150s in mythtv-setup? I seem to recall that, in
>> 0.23, mine were configured to record video at 720x480 resolution
>> with VBI enabled and variable bit rate around 2.4 Mbps, and audio
>> was mp2 192 Kbps. Perhaps changing your card's configuration in
>> mythtv-setup will let you record content that mythcommflag can
>> decode? Regards, Helen
> 
> I did some checking and found the following from mediainfo when run
> on the recording I've been testing with.
> 
> General Complete name                            :
> /var/lib/mythtv/recordings/1306_20140918170000.mpg Format
> : MPEG-PS File size                                : 1.08 GiB 
> Duration                                 : 29mn 57s Overall bit rate
> mode                    : Variable Overall bit rate
> : 5 172 Kbps
> 
> Video ID                                       : 224 (0xE0) Format
> : MPEG Video Format version                           : Version 2 
> Format profile                           : Main at Main Format settings,
> BVOP                    : Yes Format settings, Matrix
> : Custom Format settings, GOP                     : M=3, N=15 
> Duration                                 : 29mn 57s Bit rate mode
> : Variable Bit rate                                 : 4 685 Kbps 
> Maximum bit rate                         : 6 000 Kbps Width
> : 480 pixels Height                                   : 480 pixels 
> Display aspect ratio                     : 4:3 Frame rate
> : 29.970 fps Color space                              : YUV Chroma
> subsampling                       : 4:2:0 Bit depth
> : 8 bits Scan type                                : Interlaced Scan
> order                               : Top Field First Compression
> mode                         : Lossy Bits/(Pixel*Frame)
> : 0.679 Time code of first frame                 : 00:00:00:00 Time
> code source                         : Group of pictures header Stream
> size                              : 1 004 MiB (91%)
> 
> Audio ID                                       : 192 (0xC0) Format
> : MPEG Audio Format version                           : Version 1 
> Format profile                           : Layer 2 Duration
> : 29mn 57s Bit rate mode                            : Constant Bit
> rate                                 : 384 Kbps Channel(s)
> : 2 channels Sampling rate                            : 48.0 KHz 
> Compression mode                         : Lossy Delay relative to
> video                  : -211ms Stream size
> : 82.3 MiB (7%)
> 
> I believe I've since set the resolution to 720x480 but get the same
> results.  All my SD recordings play fine in mythfrontend.  I've also
> have a mix of PVR-150's and PVR-1600's.  I'm pretty sure this
> recording came off a PVR-150 though.  In my testing mythcommflag from
> myth 0.24 finds 3 commercial breaks while 0.27 finds none on this
> recording.
> 
> Thanks
> 
> Carl

Can you be more specific about the "same results"?

Do you mean you still get the numerous decoding errors, not just the one at the end (which is normal), as well as no commercial marks?

Or do you mean no commercials are being detected, but not the numerous decoding errors?

I ask because I think they are two separate problems. I have done nothing to mythcommflag that would affect the "numerous decoding errors" problem and until that one is sorted out, I would not expect mythcommflag to be able to find any commercials. I was hoping that, by changing how the card is configured in mythtv-setup, it might fix the "numerous decoding errors" problem.

Is it safe to assume that when you say PVR-1600 you mean Hauppauge HVR-1600. Do recordings made on these tuners also have the "numerous decoding errors" problem?

FWIW, I did test some old PVR-150 recordings and my version of mythcommflag worked quite well. Using the same methodology I've been using to measure accuracy, I got 71% accuracy on a recording made in 2009 and 83% accuracy on one from 2011. These recordings were made on older kernels. So I'm thinking it's time for me to configure one of my HVR-1600 cards and see if I can reproduce the "numerous decoding errors" problem. But it's going to be a few days before I can do that. It may not lead anywhere, because I would be testing with a  different kernel (3.2 from mythbuntu 12.04 vs 3.13 from mythbuntu 14.04) as well as a different tuner, HVR-1600 vs PVR-150.

While I was at it, I tested a recording made on a framgrabber type tuner in 2010 (.nuv recording made on the analog side of a pcHDTV 5500 which has since died) and my mythcommflag found one commercial break. It doesn't make sense to give it an accuracy rating because the recording was from a public tv station which is commercial free.

Regards,
Helen


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