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h2video.nl  
#1 Posted : Tuesday, November 6, 2012 5:27:43 PM(UTC)
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Hi Martin,

I have problems with getting my video and sound recorded properly. I am using BM intensity cards and feed the video input with HDMI using video and sound from the input. I then mix in VMIX using the video and a combination of desktop capture and video (overlay over a picture).

Today I recorded two sessions simultaniously with two systems and both had a problem with latency. At some point the sound and video are not synchronised anymore. For one system I stoped using the HDMI sound input and used the analogue output of the camera and input in the computer. This resulted in less problems with latency.

Occasionaly dropped frames are also occuring.

Can you give me recommendations what would be the preferred input for the recorder: do I input hdmi BM sound together with the input and record de vmix sound output (as is recommended) or do I also use the hdmi BM sound input here?

What can I do to prevent dropped frames, dropped samples and increacing latency. Why does video and sound get disconnected. Is there a way to periodically syncronise it again...

I have tested everything in the office, also did some long video tests to see if dropped frames occur after some time, and/or if sound is dropped. But not in a testing environment. But in real mixing environments this start to happen: could this be a result of the various types of input and mixing I use? Switching from video to the overlay and back?

It is a critical problem that i will have to get right! otherwise I can not use Vmix in live situations.

Please help because i have another recording session thursday.

Stefan
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#2 Posted : Tuesday, November 6, 2012 9:13:13 PM(UTC)
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Hi,

Are you adding the audio and video together as a single input or are you adding audio and video as separate inputs?
If they are separate they will fall out of sync, but if they are added together (DeckLink Video Capture + DeckLink Audio Capture) they should be fine.

Can you provide some information on your system specs? CPU, Memory, Graphics Card etc.

Also check what version of vMix you are running by looking at the version in the title bar. Is it 8.0.0.53?

Thanks,

Martin
vMix
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#3 Posted : Tuesday, November 6, 2012 10:09:51 PM(UTC)
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Couple of other points:

1. If you do not have 8.0.0.53 download vMix 8 again from the download page.
2. Try recording to "TS" instead of "MPG" as TS handles audio synchronisation better if there are dropped frames/audio.

Regards,

Martin
vMix
h2video.nl  
#4 Posted : Wednesday, November 7, 2012 12:51:34 AM(UTC)
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Hi Martin,

I will download the new version today and test it. This might be a similar problem and so similar fix.

It would be good to have some kind of notification about new bug-fixed releases: a mailing list of registered users maybe.

I prefer to use the coupled input so hdmi BM intentity video and audio. Yesterday I switched one computer to seperate hdmi and line out and use the analogue mic input on the computer and the issue was fixed. Since I had the issue on both computers I suspected a bug: one computer is a laptop with BM shuttle USB3 inut and the other a computer with BM intensity capture cards inside.

I record in MPG because I can edit the resulting file (cut the start and end sections of a presentation) without having to render the file again. So I prefer to use MPG. If not stable or reliable I can use any other format and then convert to MPG before editing.

What recording format is recommended for most stable operation?

Greetings Stefan
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#5 Posted : Wednesday, November 7, 2012 4:15:02 AM(UTC)
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Hi Stefan,

What program are you using for editing? The TS format is the best format audio timing wise when using Sony Vegas or Adobe Premiere.
I have seen the MPG format lead to audio sync issues when editing in Sony Vegas/Movie Studio.

I was confirming the coupled input because there is a sync issue if using both separately, but as you are using them together that rules out the issue.

Regards,

Martin
vMix
h2video.nl  
#6 Posted : Wednesday, November 7, 2012 5:26:39 AM(UTC)
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Hi martin,

I am running tests now and downloaded the upgrade. i was on 8.0.50 and now .53

I will also use TS for recording.

I don't actually edit the output: i just cut it up to individual presentations. The programm I use to do that is part of a simple set of video and audio editing tools called AVS4YOU. one of the tools is AVS Video remaker. This alows me to simply delete the parts I don't want (start and finish of a presentation and save it without rendering.

Anyway: if I need to record in a reliable format first and can do that for a long time (1 - 4 hours in a row) then I can batch convert to MPG and save the individual presentations later.

Just remember: I record a number of presentations in a day, yesterday I recorded 30 presentations in 2 rooms and 6 poster presentations. Just being able to separate the individual presentations without rendering saves me a lot of time and alows me to deliver the product at the place where i am recording.

In video remaker this only works (writes) with specific formats, like (and tested) with MPEG. In this way I can save 4 or 5 presentations in one set within 5 - 10 minutes!

It also works with WMV but only MPEG4 codec and VMIX only has 1 2 and 3 (am I correct).

Anyway: I would like to have your recomendation what format to write to to have absolute reliable video and audio sync and a stable rendering over a long time.

I also wil start - stop the recording in between presentations (when there is the time for it) and open the recording options and press OK to reset the latency if any... Would be great to have that under one button: so on the fly restarting a new file and resetting all accumulated latency and or dropped frames / samples.

Stefan
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#7 Posted : Wednesday, November 7, 2012 6:28:12 AM(UTC)
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hi admin and stefan,

i allways have latency when add recorded files from vmix to adobe premiere. i have in mind that in the edition process i need to unlink audio/video and manualy synchronize them. for me, it is not a problem and i can live with it, but, depending on the editing software, it may be a huge problem.

regards,
melody
www.espiritosanto.cc
h2video.nl  
#8 Posted : Friday, November 9, 2012 4:23:03 PM(UTC)
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Hi Martin,

1. I had another recording session with new version 8.0.53. The morning session was OK (no dropped frames, dropped audio samples anything) but in the afternoon I had dropped samples in de audio session. I followed your recomendation to stop recording, opening the recording session settings and press OK to clear the dropped frames and latency on the video part. But the Vmix recorder still had the dropped samples and the delay because of that and I can not get rid of them.

Do you have any idea why I suddenly accumulate dropped audio samples. maybe somthing to do with the BM shuttle getting warm or something? I restarted the computer in the afternoon to be shure that all buffers etc were cleared, and did not change anything else, used the same preset and setup routine!

I also switched to TS format, but the problem is the accumulated dropped samples in the audio section i can not get rid of or reset / clear. So I still have sound off-set.

2. Would it be better to link the BM audio input directly to the recorder in stead of putting it through the vmix mixer? I can do that by not selecting the BM audio input with the video and select that input on the recorder settings. Whould that solve anything?

Hope you can find the cuase of this misterious dropped samples.

Will send you the logfiles of today by mail.

Stefan
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#9 Posted : Friday, November 9, 2012 9:48:49 PM(UTC)
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Hi Stefan,

Could you let me know as much detail about your system specs as possible?
I've looked at the logs and do not see anything too out of the ordinary, have you tried playing back the recordings directly in vMix to see if the delay is there?
vMix by default automatically compensates for droppped frames or samples so it should not affect the final result.

As mentioned previously it could be the editing program showing the issue rather than the recordings themselves.

Regards,

Martin
vMix
h2video.nl  
#10 Posted : Saturday, November 10, 2012 5:01:12 AM(UTC)
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Hi Martin:
from the logs:

First recording:
-11-2012 8:28:08, AudioOffset: 24
8-11-2012 8:28:08, AudioEngine
8-11-2012 8:28:08, Running: True
8-11-2012 8:28:08, SampleRate: 48000hz 16 Bit
8-11-2012 8:28:08, MixingErrors: 0
8-11-2012 8:28:08, Streams
8-11-2012 8:28:08, Stream0
8-11-2012 8:28:08, Samples: 32372
8-11-2012 8:28:08, DroppedSamples: 0
8-11-2012 8:28:08, Latency: 2

last recording:
-11-2012 16:31:07, AudioOffset: 19
8-11-2012 16:31:07, AudioEngine
8-11-2012 16:31:07, Running: True
8-11-2012 16:31:07, SampleRate: 48000hz 16 Bit
8-11-2012 16:31:07, MixingErrors: 0
8-11-2012 16:31:07, Streams
8-11-2012 16:31:07, Stream0
8-11-2012 16:31:07, Samples: 283613
8-11-2012 16:31:07, DroppedSamples: 58
8-11-2012 16:31:07, Latency: 2

The problem is in the dropped samples - isn't it!?
Stefan
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#11 Posted : Saturday, November 10, 2012 5:11:22 AM(UTC)
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Martin,
My system setup:

HP laptop (HP DV7-6B60ED 17.3FHD/I7-2670/8/160SSD+5) with SSD and HD and intel i7 second gen
USB3 chip is nec with latest renesas drivers as recommended by BM
I use one BM shuttle connected to the USB3 port.
laptop with desktop capturing connected.
I only use one audio stream from the BM
Camera connected with HDMI - capture video and sound

System load is only 17% and rendering time 13 ms on average.

When I accumulate dropped samples I can not reset the audio engine to forget about those dropped samples, so the system is comensating for the dropped samples with an audio offset? Is that how it works.

Could the problem be in the combined overlay with video and desktop capture combined and switching from video to overlay?

I made 10 recordings OK (see log files sent and look at the recording timestamps) and then at some point the system runs out of sync. Maybe something accumulating exponentially (2ms 4ms 8ms 16ms etc etc...)

I did not change anything during the day: used exactly the same system, setup. connections, cards, presets etc etc).

greeetings Stefan
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#12 Posted : Saturday, November 10, 2012 6:04:27 AM(UTC)
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Thanks for the info.

In the recordings where you see a sync issue, is the audio too early or too late?
If it is too early (hear sound before the video) then it is *possible* it is a Audio Engine issue, but if the audio is delayed then the issue must be somewhere else.

The audio engine works by receiving all of the audio from the various inputs and then mixing it all together.
If an audio input is sending too many audio samples (i.e the BM shuttle sends us 1.1 seconds of audio when only 1 second has elapsed) then it will drop some samples
to ensure that there is no delay. So when you see dropped samples in the log that is actually a good sign as vMix is making sure all audio is arriving when it should be.

So based on that explanation, if the audio is delayed it may be caused somewhere else, such as in the playback or editing program. (which is why I have suggested using TS and trying playback in different programs to see if the issue is there)

Couple of other ideas to try:

1. Try recording using AVI and the DeckLink MJPEG Compressor. Not only is this the highest quality format it is also the most widely supported format for video editing.
2. Are you always recording direct to HD? I've seen some SSDs randomly pause on occasion causing all sort of strange issues.

Regards,

Martin
vMix
h2video.nl  
#13 Posted : Saturday, November 10, 2012 6:35:15 AM(UTC)
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Thanks for the awnser Martin,

The sound becomes increasingly late: sometimes a delay of 3 seconds or more.

I do not edit: just view the video and upload to youtube. The delay is already in the recording.

I am trying to replicate the problem. maybe it is somewhere in the BM driver, the cable or the sequence to connect and hook up things (hdmi, Shuttle, VMIX capture etc). It should all be in line...

I just recaptured the last presentation and changed the BM USB 3 cable. One dropped frame and no dropped samples, but some black frames in the video...

One issue for you to awnser: once the sound recorder has registered dropped samples and the recording is reset and started agian: the dropped samples are still there. Does this add to the delay of the new recording? Is there a way to reset that, other than starting up vmix all together?

Stefan
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#14 Posted : Saturday, November 10, 2012 7:27:18 AM(UTC)
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The Dropped Samples mentioned in the "Audio Engine" section of the log is unrelated to the recording. It is a total
number of dropped samples since vMix was started and the recording does not use this information to determine how it is recorded.
h2video.nl  
#15 Posted : Saturday, November 10, 2012 7:59:42 AM(UTC)
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martin. I mean the dropped samples reported under the i button of the recording section in vmix. When I look at that section during recording I can follow the number and progression of the dropped frames.

When i restart a recording the dropped frames etc are cleared as you explained. The recording starts with everything set to 0. But not the sound recording section. The number of dropped frames reported under i on the master recording meter still will report the dropped samples. I presume vmix will take this in account.

Thus a noticable delay is heard during recording on the monitor / headphone: the sound is off and delayed.

The logfile only reports the end result.

i button reports start and inbetween progression of the dropped samples as does the i button next to the recording button give me a running status on droppd frames delay etc.

So I am not referring to the log file...

Hope this clears this discussion,
Stefan
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#16 Posted : Saturday, November 10, 2012 9:50:22 AM(UTC)
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Hi Stefan,

The information provided in those windows is what is saved to the log file at the end of the recording.
The sound statistics you mention are not applicable to the recording itself.

If you are hearing the delay on the headphones than it does indeed sound like the delay is in the bm shuttle itself in which case if you right click the capture input
and select Reset, this might help. You could also try the "Blackmagic WDM Capture" option with built-in audio selected as this a new alternative BM has provided with the recent drivers.
The resolution for this option is set within the Blackmagic Control Panel. "Set Default Video Standard as"

If the delay in your headphones does not change after resetting the capture device then the problem might be with the camera or audio source.

Regards,

Martin
vMix


h2video.nl  
#17 Posted : Saturday, November 10, 2012 12:21:07 PM(UTC)
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Thanks Martin,

I have switched to the WDM capture: looks promising ! I am in the midst of re-capturing some presentations so enough practise.

Also thanks for the reset tip: I didn't discover the use of this button yet.

If everything is working OK we can close this thread.

greetings
Stefan
h2video.nl  
#18 Posted : Tuesday, November 13, 2012 1:12:17 PM(UTC)
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Hi Martin,

I have succesfully reprocessed all files using the WDM capture. I have also upgraded the Black magic Design drivers to the latest versions. I will also keep an eye on updates for the NEC Renesses (USB3) drivers.

I still have some issues with black frames once in a while.

I have a new recording this thursday, so hope all will go as planned.

Greetings,
Stefan
h2video.nl  
#19 Posted : Monday, November 19, 2012 7:17:01 AM(UTC)
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Update:

The recording was good, the presentations were online the same day at 21.00h. No problems with delay or latency.

But I still have issues with black frames. I tested today (see also my other post about dropped frames related to an external monitor).

I switched the camera (panasonic HDC-SD700) from 1080i to 576p output over HDMI and the input to PAL on the BM intensty shuttle.

I have to really test for a long period, but I did not notice any black frames anymore. So I guess, bringing down the capture resolution (if you don't really need it as I do) is solving the problem. I think it has something to do with the write speeds on my laptop (SDD !! but anyway...).

Test recordings had zero's all over for dropped frames, audio samples, and latency (1 or 2 so the recording is synchronized)

I also have a computer with BM capture cards and will test that system later for settings and black frames and input resolutions etc.

I also changed the audio capture resolution to 41k from 48k, and this reduces the dropped samples (to zero).

I have some more (long) recordings this week so I will have some more time testing.

PS increasing the buffersize did not change anything.

Greetings,
Stefan
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