Sound but no image after tuning on TV channel

Discussion in 'General Support' started by Stéphane Lenclud, December 19, 2015.

  1. Stéphane Lenclud
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    Sometimes after starting MP the first tuning to a TV channel results in a black screen with only the audio playing.
    Switching channel works but you still don't get video, only audio until you restart MP.
    Logs attached.


     
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  3. mm1352000
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    Looks like slow decryption (TsReader log shows the stream is encrypted - "PES ... 0-0-1 fail" - for approximately 2 seconds after tuning is apparently successful) may be causing problems for the codecs you're using (MS DTV/DVD). The EVR video renderer never appears to draw any frames. In other words, it looks like the video frames are lost somewhere between TsReader and EVR... and the only thing there is the video codec. Such a problem can only be solved by resetting the video codec (ie. stopping and restarting TV, or reopening MP as you said).

    In short: try different codecs.
     
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  4. HTPCSourcer
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    I have the same TV hardware as Stéphane and experience the same occasional issue. However, it sometimes also happens when playing recordings, which (I believe) are already decrypted.

    I am bound to using a combination of MS-DTV and LAV on one particaluar machine (HTPC1). Using only LAV for TV causes very high CPU load. I've tried all possible options of hardware acceleration. Other than the occasional "no picture" there is no problem, so I can live with it.
     
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  5. mm1352000
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    Recordings are "decrypted" in the same way that the live TV stream is "decrypted" before it is written to the time-shift file. As such it's entirely possible for the same problem to happen in the same way. Encrypted PES packets can be "baked into" the recording.

    Why do you think they are your only choices?
    What about FFDShow DXVA, Cyberlink, CoreAVC, DivX etc.? There are plenty of other possibilities. ;)

    ...and to be clear: you consider this unacceptable?
    (Using CPU for h.264 decoding is a valid option.)
    ...and have you reported this problem to Nev?

    If MS DTV/DVD can use DXVA then so can other codecs. Troubleshooting such problems in such detail is beyond me, but I encourage you to report the problem to Nev (the LAV developer) on Doom9 Forum if you haven't done so already.
     
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  6. HTPCSourcer
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    Unfortunately, except FFDShow, you have to pay for them. Also, no point in spending even more time on MP than I do now.

    Yes, I do. TV is unwatchable.

    No, it's not.

    Frankly, I have neither the time nor really the interest to expand activities into other forums.
     
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  7. mm1352000
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    Wow, that's an overwhelmingly negative response. Please remember I'm only trying to help! ;)

    In order to avoid upsetting you (as it seems I managed to do with my last response - sorry), please can you briefly clarify what you hope to achieve by responding in this thread. I'm confused because on one hand you say you can live with the problem, but on the other hand it seems like you want a solution (...but only if it doesn't require any time/effort?).

    For the record that's not entirely true. There's a free version of the DivX pack which comes with a fully functional h.264 video decoder (DXVA 2.0 only => no DXVA on XP). Even older versions of the Cyberlink h.264 video decoder can be acquired free and legal [for example] by installing Twinhan's DigitalTV software.

    Are you referring to your "Baytrail" system only?
    I guess either way I'm a little surprised. Even my PC (first gen 2006 Intel Core 2 e6600 dual core 2.4 GHz) is able to do 1080i h.264 decoding without DXVA @ ~60% CPU load (LAV, CoreAVC, DivX).

    Some people don't have a choice. We'll have to agree to disagree on this point. :)

    Okay, so I assume from this response that you have not reported the problem, which shows that you really are willing to live with the situation. That's fine. My comment was only an "encouragement"/suggestion. Feel free to ignore it. :)
     
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  8. HTPCSourcer
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    My sole intention posting here was to say that Stephane's observations are not unique.

    I only have these problems on one single system (HTPC1), which is not the Baytrail CPU. The latter is running 100% on LAV. Interestingly MS-DTV on that system is leading to unwatchable TV, choppy picture etc., but it works well with LAV.

    I am not upset, but was irritated about the "consider this unacceptable". I would not have mentioned high CPU load, if this wasn't an issue.
     
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  9. mm1352000
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    Okay, thanks for the clarification.

    Sorry that I irritated you. That question was a poorly worded attempt to try to understand whether the situation was:
    1. DXVA not working => high CPU usage => dropped frames (ie. TV is not really watchable).
    2. DXVA not working => higher CPU usage than when DXVA is active... but no dropped frames (ie. TV is watchable).
    I should have simply asked if the CPU usage was leading to dropped frames.

    From what you said:
    1. The black screen issue only affects HTPC 1.
    2. DXVA scenario 1 applies to HTPC 2 (Baytrail CPU) whereas DXVA scenario 2 applies to HTPC 1.
    Therefore if I've understood correctly, in my opinion it would technically be possible (though from your perspective: strongly not preferable) to temporarily use other video codecs including LAV on HTPC 1 to determine whether the black screen issue does or does not apply to all codecs. If you're not willing to test then hopefully Stéphane will be able to perform equivalent tests to acquire the same information. My hypothesis is that at least some codecs including LAV would not be affected.
     
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  10. HTPCSourcer
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    Correct

    No.
    HTPC2 (Baytrail) works flawlessly with LAV codecs - but surprisingly not with the MS-DTV one, which causes heavy stuttering.
    HTPC1 in combination with LAV for h.264 kicks CPU usage to 80% whereas MS-DTV runs at 15-20% load, including 1080i content.

    In principle yes. However, HTPC1 is the main machine in the living, hence utilized a great amount of time, which limits the available test time window. Also the black screen issue is not happening every time and I have not figured out a scenario that would reliably trigger it in all cases.

    I am quite confused by the different behavior of MS-DTV and LAV on HTPC1 and HTPC2.

    All these codec issues originate from Microsoft's decision to remove the MPEG2 support from Win 8 and 10. Sadly LAV does not appear to be the perfect solution either, if I am getting the "Known Issues" in http://forum.doom9.org/showthread.php?t=156191 right:
    That said, why does it work on HTPC2 then?
     
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  11. mm1352000
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    To be clear: you mean that LAV DXVA works so CPU usage is normally relatively low (< 25%), right?
    (...but as you said previously, if you would disable DXVA for any reason then CPU usage would jump to 100%?)

    I can't explain this.

    Yes, this is exactly the result I'd expect if LAV DXVA is not working as it should. I'd expect MS DTV and all other codecs would give approximately the same CPU usage with DXVA disabled. So, the question for HTPC 1 is: why is LAV DXVA not working? I'm not able to answer this. Nev would surely be able to help, but you have to be willing to take the time to ask him etc.

    Yes, I understand. If the black screen issue happens relatively frequently (every couple of days?) then perhaps an alternative way of testing (without being able to trigger) would be to switch over to LAV for a week and see if you notice whether the issue is gone or not. Having said that, it's possible that DXVA being enabled or not may make a difference to the issue.

    Anyhow, whether and what you want to test is completely up to you. :)

    Again, I can't explain this.
    Assuming you're using the same driver, MS DTV/DVD and LAV versions and LAV configuration the only possible causes of differences I could suggest would be:
    1. Something related to differences in power savings modes (eg. CPU turbo behaviour etc.). I've seen reports of people solving stuttering problems by opening an internet browser. That was enough to stop the CPU is bouncing between lower and higher power states, which was causing trouble for the video decoding.
    2. Different DXVA modes (LAV vs. MS DTV/DTD). For example, MS codecs will be using DXVA 2.0 whereas depending on configuration LAV could be using Intel QuickSync. Maybe something about QuckSync (which MS codecs don't support

    I'm confused; I don't follow your train of thought. I thought we were talking about h.264/AVC not MPEG 2. :confused:
    h.264 decoding requires significantly more processing power than MPEG 2 decoding. I would have thought both your HTPCs should be more than capable of decoding SD MPEG 2 without any trouble regardless of DXVA. They may have problems with HD MPEG 2... but AFAIK HD MPEG 2 is only used in Australia, USA and maybe Canada.
     
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