Sometimes only records audio

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Sometimes only records audio

Post#1 » Tue Mar 14, 2017 4:08 pm

Occasionally some of the recordings have only audio. The video is black, and when I start to fast forward through the black, Media Center will get very unhappy; it will stop fast forwarding, or come up with an video error, or it will just hang and spin. So my guess is that it isn't just missing the video but it is some type of corrupt recording.

I haven't been able to figure out what has been in common with the bad recordings. The same tuner will record properly a few hours earlier. And the channel it fails on are random and after a random number of successful recordings, so I haven't been able to reproduce the issue at will.

I've already replaced the CableCARD and the symptom is still present. My next step is to replace the tuner card itself. Hard drive I guess could be a variable; I've replaced that, and I don't see any obvious errors in the Event Log that indicate a problem there, though not necessarily the most reliable for hardware type failure.

Any input would be appreciated.
DFox
 
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Post#2 » Tue Mar 14, 2017 11:45 pm

The only time I have had recordings with audio but no video is a couple times when I was recording "Big Brother After Dark" on POP TV.

If you did a 411-info to display diagnostics in WMC, the video codec would be "unknown" (or something like that, my memory fades).

If I saw this was happening while it was recording and I stopped and restarted the recording, the new recording would be fine, so it was a really strange problem.

Like I said, it only happened twice and has never happened on any other show/channel.

This doesn't sound exactly like the problem you are having since it happens on random channels/shows, but I would guess you are having the same issue with an "unknown" video codec.

When I played the affected video, the audio would play and the screen would be black, but I would see strange artifacts on the screen from time to time. Eventually the video would just hang up and not play anymore (I think I needed to exit WMC and restart it to get the video (audio?) to play again).

My guess as to what the problem was was with the way the video was encoded. Perhaps there was some sort of issue that only manifested itself when you started recording at a certain time within the video stream, but I have no idea what that could be or how it could be resolved other than complaining to the network or cable company (but unlikely they would be able to do anything).
Space
 
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Post#3 » Wed Mar 15, 2017 1:47 am

Thanks for the response. I didn't go into too much detail of the symptoms, but your description matches mine, with it basically black for most of it with occasional artifacts until Media Center finally chokes.

I say that it is random channels and times because it happens on different channels and times. But now that you mention it, one channel has many recordings, like an average of a few times per day, and it never has had a problem.

Good call with suggesting the 411; I didn't think to do that because I was heading down the path of a hardware issue. For some reason I kept three bad recordings from the same channel and show, two of which I recorded prior to my many Media Center resets, so the channel number shows 502.0 instead of 502. Two of the three recordings say "(not specified)" for the video codec, and the one with the proper channel displayed says H264. I wish they all had the same for troubleshooting purposes.

So frustrating to sit down to a bunch of black thumbnails.
DFox
 
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Post#4 » Wed Mar 15, 2017 2:06 am

It literally just happened again so I was able to do debug on it and it said video codec "(not specified)". Then I stopped the recording and recorded it again, this time its fine and video codec says MPEG2.
DFox
 
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Post#5 » Wed Mar 15, 2017 4:13 am

Yes, I think it was "(not specified)" on mine too, I couldn't remember the exact wording...

One other hypothesis of what was happening was that the show airing before the one I was recording had issues with the encoding, and since the recording started a little before the prior show had ended, it was this show that was messing up the recording. So when you stopped and re-started the recording it was no longer affected. I doubt that is the reason (I am sure it is much more technical and esoteric), but who knows?

I never really got a chance to test anything because after the first time it happened I just thought it was a fluke and hoped it wasn't going to happen again, then after the second time I kept a closer eye on things but it never happened again... But to be honest, I am not sure what I could have done to troubleshoot if it did keep happening...

I would think you would need someone to analyze the video to see what improper information is being put in the video stream (the audio stream is completely separate and that continues to work). If you have a small recording that has the problem (perhaps the one you just made) you can upload it somewhere and find some experts (not sure who) who may be able to analyze it to see what may be the problem. There may even be a way to fix the video by doing a binary edit of some critical data in the header of the video or something like that, since I am sure the stream itself is probably fine (since stopping and restarting the recording of the stream works).

But this is all just guesses, I really don't know much about this stuff.
Space
 
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Post#6 » Wed Mar 15, 2017 1:38 pm

Unfortunately the recording it failed on last night was one of the few FiOS channels that is copy protected, so probably not a good sample. If you have a suggestion of how to truncate one of my other 30 minute wtv files without impacting the encoding (or lack of) I can do that. But like you said, I don't know who I would send it to for analysis.
DFox
 
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Post#7 » Wed Mar 15, 2017 2:58 pm

I have a similar issue that I posted under the thread "Mpeg4 issue changing channels" If I switch from an Mpeg4 channel to a "copy once" Mpeg2 channel I get the audio only issue. If I first switch from the Mpeg4 channel to an Mpeg2 channel "copy freely" and then to the Mpeg2 channel "copy once" everything is fine. Could this be your problem depending on the "last tuned" channel? I am using a Win 7 64 bit system.

I believe this is a WMC issue and we are stuck with it since WMC is dead code.
Paw Paw
 
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Post#8 » Wed Mar 15, 2017 5:02 pm

I believe that is probably a separate issue (although it may be related, what do I know?).

I have it too, changing channels (live TV) between MPEG4 and MPEG2. But I have never seen that issue when recording a channel as opposed to live TV (I've only had the issue recording a single MPEG2 channel). I am guessing there is a speed optimization being used when using live TV (to make channel surfing faster) and that optimization doesn't properly "reset" whatever needs to be reset in order for it to transition cleanly between MPEG2 and MPEG4 (it was probably never tested properly due to the scarcity of MPEG4 channels at the time it was being developed, I am frankly surprised that MPEG4 works at all).
Space
 
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Post#9 » Wed Mar 15, 2017 8:13 pm

While the show is recording, it seems one way to identify it is problematic is to view the video codec as "not specified" in the 411 Info. Other than obviously it being black. I'm wondering that if while it is recording there is some way to identify the video codec in the file itself, or somewhere else. The reason I'm asking is that if there was a programmatic way to identify this, then I could monitor and parse every new recording on the fly to look for this condition, and then take action like stop it and record it again. The trigger is straight forward since every recording raises an Event Log entry, and stopping and starting specified recordings is probably relatively straight forward (though I've never tried). So the missing piece would be the identification of the bad recording at the time it starts recording.

The other option is that if we can figure out exactly under what circumstances it happens, like after viewing live TV or whatever, then when that happens insert a dummy manual recording.

Another option could be to constantly monitor for any new recording and then for each of them add a dummy manual recording before it no matter what, and deletes itself right after.

I'm slowly becoming doubtful there is a real solution for this so a hack workaround might be the only option.
DFox
 
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Post#10 » Wed Mar 15, 2017 9:34 pm

Yeah, the problem is that WMC does not know there is any issue while it is recording the stream. As far as it's concerned, everything is fine.

It is probably possible to have an external tool look at the codec in the saved stream, but I would think that would only work if it was not copy protected (and therefore not encrypted).

I really don't know why this happens, but I tend to lean more towards the stream itself having bad data in it.

I believe that the stream must send information about what is in the stream on a periodic basis, as WMC needs to know what the contents of the stream are in order to play it properly. Perhaps certain streams are sending bad data for some of these periodic updates and WMC is just using the first update it gets when it starts recording (even if other updates that contradict that one come later).

If the first update it gets happens to be the corrupted one, then you get a bad recording. That's why I suggested having someone who knows about video streams to look at a sample video file to see if they can determine if the stream has invalid data in it.

Of course I really have very little knowledge of any of this so this is all just speculation.

Another thing you can try (for non-copy protected recordings) is to right click on the file and "Convert to DVR-MS" and see if that does anything. I am guessing it will fail, but it is worth a shot. Maybe also try other video converters/analyzers/repairers that may be found on the Internet.

Just brainstorming here...
Space
 
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Post#11 » Wed Mar 15, 2017 10:11 pm

(I was typing this before I saw your post.)

Ok, new information. I ran the bad recordings through MCE Buddy and the converted mp4 file plays fine. This seems like pretty conclusive evidence of something, I just don't know exactly of what though. Maybe something with HDMI, but would that explain the black thumbnails and the video codec not specified? Unless the tuner is analyzing the entire HDCP handshake at the time of the recording? Even if the TV and AVR are off? Hmm, maybe that's my variable, recordings while the TV is on versus recordings while the TV is off.
DFox
 
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Post#12 » Wed Mar 15, 2017 10:34 pm

I doubt HDMI (HDCP) has anything to do with it, due to the things you mentioned.

HDCP does not come in to play when the video is recording, only when you are playing the video and outputting to the TV.

It's good to know that converting the video file works to make it viewable. I'll have to remember that next time I have this problem.

I think that this is more evidence that there is just something wrong with one of the periodic updates that the network is sending out within the stream. If you happen to start recording just before that bad update is sent, WMC uses this update for the entire video.

The WMC player (and Windows Media Player), probably just look at the first indicator in the stream that tells it what the video codec is. Other players and video converters may be more robust and are able to see the other indicators and can play/convert the video.

Another thing you can try is to play the video with other players (VLC, etc.) and see if they are able to play them (only non-copy protected ones, though).
Space
 
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Post#13 » Thu Mar 16, 2017 1:22 pm

Space, the biggest problem with your explanation is that it would render my situation hopeless :-)

But seriously - yesterday I only had a quick look at the converted mp4 video file. But today I (tried to) watch it and it is very stuttered. I also tried to play the wtv file through VLC and it too only played audio and said: "Codec not supported, VLC could not decode the format 'h264' (H264 - MPEG-4 AVC (part 10))". When I tried to convert to dvr-ms it says "WTV Converter cannot concert the file from .wtv to .dvr-ms format because the content is not compatible with the .dvr-ms file format." I confirmed the other good recordings can convert. So yeah, the recording file is messed up, technically speaking.

But I am desperately trying to still hold onto the hope that it is something hardware related. If it is something wrong with the provider's encoding message, then wouldn't it impact every Verizon Media Center user? Maybe it's a local leg of Verizon, which might explain shows with commercials in or before them, but I had this symptom on Showtime. Or maybe it's just bad luck that the particular shows that we are recording have this issue? But the show and channel range is varied, and the shows are relatively mainstream and not obscure, and it happens often.

In your opinion, is it poooosible it is hardware? Maybe the tuner card? Or bad luck that the replacement CableCARD was also bad? Or possible something about my specific Verizon feed to our home or pairing is bad?
DFox
 
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Post#14 » Thu Mar 16, 2017 1:27 pm

Since there's been a shift from MPEG2 to MPEG4 with the cable companies, is it possible that your video card, and drivers, do not support MPEG4? I have an Nvidia 650ti video card and do not have these issues.
mldenison
 
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Post#15 » Thu Mar 16, 2017 1:34 pm

My rig is pretty old, so very possible. But if that were the case I'm not sure how to explain that first it starts recording a bad version. Then I stop the recording and start it again and then it works. I would think if the video card didn't support it then it would be bad all of the time? And watching it with Live TV first and then recording it works too. Also, if the TV is off, does the video card play a role if it is just recording? mldenison, do you have Verizon service?
DFox
 
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Post#16 » Thu Mar 16, 2017 2:51 pm

No, I'm on Comcast. I was just conjecturing. A few years ago I was having the same issue but just with my Ceton Echos - audio but no video - and I went with a new video card. The problem disappeared so there must be some connection, for me, with the video card and drivers. I wish someone nails it down for you.

Mort
mldenison
 
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Post#17 » Thu Mar 16, 2017 2:59 pm

Thanks Mort for the input. It does seem like it is possible because the symptom of the black plus artifacts and audio seems similar to symptoms of playback for other issues like yours. Actually Ceton Support responded to me by saying that it is probably HDMI/HDCP related. But as Space mentioned, the recording file itself is messed up and HDMI/HDCP and the video card should only be related to playback. So I'm hoping that through some unknown (to me) mechanism the video card comes into play during the recording process, or simply a bad Ceton tuner card or CableCARD.
DFox
 
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Post#18 » Thu Mar 16, 2017 3:20 pm

DFox wrote:Space, the biggest problem with your explanation is that it would render my situation hopeless :-)
Not necessarily hopeless. Maybe Verizon is making some changes to their system and causing the issue (I also have FiOS, by the way). If that is the case, then maybe more people will see this problem in the future (which VHO are you in on FiOS?, I'm in VHO7, Northern NJ)
DFox wrote:But seriously - yesterday I only had a quick look at the converted mp4 video file. But today I (tried to) watch it and it is very stuttered. I also tried to play the wtv file through VLC and it too only played audio and said: "Codec not supported, VLC could not decode the format 'h264' (H264 - MPEG-4 AVC (part 10))". When I tried to convert to dvr-ms it says "WTV Converter cannot concert the file from .wtv to .dvr-ms format because the content is not compatible with the .dvr-ms file format." I confirmed the other good recordings can convert. So yeah, the recording file is messed up, technically speaking.
Interesting that VLC thinks it is h264, was this one supposed to be h264 or MPEG2? If it is h264 then WTV converter would not work as it only supports MPEG2. Too bad that the MCE Buddy converted video did not work.
DFox wrote:But I am desperately trying to still hold onto the hope that it is something hardware related. If it is something wrong with the provider's encoding message, then wouldn't it impact every Verizon Media Center user? Maybe it's a local leg of Verizon, which might explain shows with commercials in or before them, but I had this symptom on Showtime. Or maybe it's just bad luck that the particular shows that we are recording have this issue? But the show and channel range is varied, and the shows are relatively mainstream and not obscure, and it happens often.
It could be hardware, but as I have tried to stress here, I really don't know much about this stuff. Like I said it could just be something Verizon is testing in limited situations or areas.
DFox wrote:In your opinion, is it poooosible it is hardware? Maybe the tuner card? Or bad luck that the replacement CableCARD was also bad? Or possible something about my specific Verizon feed to our home or pairing is bad?

My opinion is not worth much in this situation, but yes, I suppose anything is possible. But I fear it is not. As I've indicated, it has only happened to me twice on the same show on the same channel. So if it is the same cause as your issue, then it would appear unlikely to be a hardware issue (although I suppose it still could be). Perhaps you can try to see if others in your same VHO with WMC are having similar issues?
Space
 
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Post#19 » Thu Mar 16, 2017 5:13 pm

I also have FIOS and I occasionally experience this problem with some channels. It frequently happens with Showtime. It almost always goes away (at least temporarily) after restarting the ehrecvr service. I haven't proved this yet, but it seems as if this only works if you've tuned to the particular channel at least once. The good news with Showtime is that the shows are repeated often, so once WMC is not busy recording I do the restart and then I can reschedule the recording for another showing.
mskenny
 
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Post#20 » Thu Mar 16, 2017 6:06 pm

Thanks mskenny for sharing. It makes me feel slightly better that my situation isn't totally unique, I guess in a commiserating sense.

Maybe it is bad luck that the shows I record often are on channels that this could happen to. However, as I mentioned before, one channel records essentially every day a few times a day and so far never had the issue. I've been doing what you do: notice the black thumbnail, find another time it is on and manually record that, and delete the bad one. It's just that I need to then babysit it almost every night to make sure I can reschedule it within the time it will show again. And the network TV shows most of the time don't have another airing.

How long have you been having this problem? This started for me maybe two months ago. Where are you located? I'm in VHO5 Downstate New York.
DFox
 
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