Trouble with sound sync

[JohnRVSP]

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1. I have a video capture device that captures video from a HDMI source.
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https://www.cloner-alliance.com/hdmiclo ... suite.html
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It is inserted between the source (cable box) and the display (Samsung TV).
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It saves in MP4 format to USB Device-(SSD with USB->to->SSD adapter).
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Its data plays fine on WMV without any complaints.

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MediaInfo reveals the following file format data...…


Original:
General
Complete name : M:\Encode_45.mp4 <-----------------------------------Says MP4
Format : MPEG-4 <------------------------------------------------------------Says MP4 -- I rename this to *.MOV <--MOV
Format profile : Base Media……………………………………………………..……. Because of this thread--> viewtopic.php?f=1&t=65100 which finally yielded success!---kind of--

Codec ID : isom (qt ) <--------------Possible problem/discontinuity Identified by LATA -->Really QuickTime? -- NOT MP4??
File size 15.2GiB Duration : 6 h 12 min
Overall bit rate mode : Variable
Overall bit rate : 9 204 kb/s

Video
ID : 2
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L3.1
Format settings : 1 Ref Frames
Format settings, CABAC : No
Format settings, RefFrames : 1 frame
Format settings, GOP : M=1, N=120
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 6 h 12 min
Bit rate mode : Variable
Bit rate : 9 204 kb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 59.940 (60000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.102
Stream size : 14.7 GiB (97%)
Language : English
Codec configuration box : avcC

Audio
ID : 1
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 6 h 12 min
Bit rate mode : Variable
Bit rate : 192 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 505 MiB (3%)
Language : English
Default : Yes
Alternate group : 1



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I am trying to down-scale the video to about 2k data rate from 10K data rate to save space,
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and re-encode to actually play on my Samsung TV using these settings....

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MPEG-4 Files
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24 bits, 1280 x 720, 30 fps
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Frame-based
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H.264 Main Profile Video: 2000 Kbps
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48000 Hz, 16 Bit, Stereo
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MPEG AAC Audio: 192 Kbps


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The troubles are:
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1. After about 1 hour of video that is re-encoded, the sound is beginning to be noticably out of sync....
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2. If I edit commercials out, The sync problem becomes worse--faster!


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I thought I might split the audio away from the media and push the tail end forward 1/2sec to 1 sec to resynchronize the audio,
but it seems I can no longer split the audio away (I used to could when I had 2 or 3 cameras creating original content, I would sometimes use audio from camera A and sometimes from camera B, which ever I thought had the better output, and suppress the others at that particular time.

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I can not seem to split the audio away or have forgotten how to do so

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SO

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Does anyone have any ideas as to:
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1. Why is there a sync problem in the first place?---the original data plays fine
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2. Any good easy solutions on how to fix the audio sync issues?


Thanks,
John

[tletter]

I can not seem to split the audio away or have forgotten how to do so

Highlight the clip in question and select 'Split audio' on the context menu.

Why is there a sync problem in the first place?---the original data plays fine

I've experienced this as well. It seems that VS doesn't always correctly position the video and audio tracks whilst rendering (see viewtopic.php?f=1&t=65246).

Any good easy solutions on how to fix the audio sync issues?

As the audio was shift right towards the end of the rendered MP4, I shifted the audio clips left towards the end of the VSP. However, this is not a good solution and shouldn't be required.

tletter
https://www.youtube.com/user/tletter

[weaver]

Hi John

What you are planning to do is already out of recent possibilities. The stream what are you getting over cable in BW of cca 10 Mbps is already heavily compressed ( by a cable provider or stream distributor). This video in studio was at least 20 Mbps or even more. That means your stream is already very "empty" (GOP M=1, N=100) means that only every 100th frame contains original picture material, the another 99 frames cary just the differences from the pervious and next frames and some other information.
When you try to recompress to 2 Mbps the compressor will try to recalculate the 99 critical frames ( containing just the difference information). This content is very often beyond the internal limits (thresholds) of the compressor and will simple drop the frame ( as noise etc). That will cause the sync gap and the audio track will not follow any more the compressed video.
The commercials in the stream are inserted in two different ways. It is done in the studio, ie the transmitted stream is a complex edited program including the commercials, recompressed for transmission (10 Mbps). On some networks the centralized commercials are replaced with local commercials. In this case in original stream there are just flags (DPI) which switch the encoder in the headend from the main input to the local source, and replaces the central commercial part with a local one. In this case the synchronity is not really garanted. The local commercial has no technical "relation" to the main stream, just the length is usually adjusted ( sometimes not even that). That means in your recording there will be a technical drop (notch) in the stream, ie if you want to edit this and compress it will again destroy the sync relation with audio.
Do not forget in the digital world what you see and hear has nothing to do with the real time. It is delayed and manipulated ( converted) for several seconds, not only for the long transmission ways ( satellite) but also in many technical equipment in the transmission chain. You do not see these processes and you also do not know how long the signal is delayed and reconverted in many hubs in the chain. What you get at home is mostly the minimum what can be restored in home equipment as picture and audio, but is not enough for any further processing.

[JohnRVSP]

I can not seem to split the audio away or have forgotten how to do so

Highlight the clip in question and select 'Split audio' on the context menu.

tletter
https://www.youtube.com/user/tletter

Tletter,
Thanks for the reply,
I have 'Right Clicked' and selected 'Split Audio' and an audio track has appeared, but there is no "SIGNAL" - "HEART BEAT" visible to help sync with visual cues....

How can I "SEE" the sound?
Can I "SEE" the sound?

Thanks for your thoughts Tletter.

The stream what are you getting over cable in BW of cca 10 Mbps is already heavily compressed ( by a cable provider or stream distributor). This video in studio was at least 20 Mbps or even more. That means your stream is already very "empty" (GOP M=1, N=100) means that only every 100th frame contains original picture material, the another 99 frames cary just the differences from the pervious and next frames and some other information.
When you try to recompress to 2 Mbps the compressor will try to recalculate the 99 critical frames ( containing just the difference information)………

Weaver,
Thanks for your reply,
Sometimes VSP works perfectly even out to 2 hours...no visible sync disparity.
1. Why does it work perfectly sometimes and
2. With errors other times?

Lots of times the source data is from the same source ("STARS") movie channel, and Same cable provider, so,
1. Shouldn't my source data streams be processed, compressed, encoded, decoded, and decompressed the same, similar program(Movie) to similar other program(Other Movie)
2. Shouldn't VSP handle the source data the same, program to program?
3. Is there a way to force VSP into submission?

The commercials in the stream are inserted in two different ways. It is done in the studio, ie the transmitted stream is a complex edited program including the commercials, recompressed for transmission (10 Mbps). On some networks the centralized commercials are replaced with local commercials. In this case in original stream there are just flags (DPI) which switch the encoder in the headend from the main input to the local source, and replaces the central commercial part with a local one. In this case the synchronity is not really garanted. The local commercial has no technical "relation" to the main stream, just the length is usually adjusted ( sometimes not even that). That means in your recording there will be a technical drop (notch) in the stream, ie if you want to edit this and compress it will again destroy the sync relation with audio.

I usually cut commercials maximizing the black "No Signal" area around the commercial,
It makes for a few seconds of black between scene changes rather than instant switching between scenes.

1. Shouldn't this editing style remove the "DIFFERENT FORMATS" commercials may have keeping the actual "Kept Data" the "Same Type and Specification" cut to cut?
2. Can I see the data "Type and Format" as I make my cut points to reduce-eliminate the "DIFFERENT" data types in the final data stream?
3. Is this something I could even do in the first place?

4. Is there an easy way to fix the sync on the data I have already down scaled without completely re-encoding again? Is there a "FAST" encoding setting in VSP--Maybe "KEEP SAME PROPERTIES" vs "Full RE-Encode" again?
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Thanks for your thoughts Weaver

[tletter]

Can I "SEE" the sound?

You can "see" the audio by clicking on the 'Sound Mixer' icon as shown in the image below.

tletter
https://www.youtube.com/user/tletter

[weaver]

John, it is not easy to answer your questions. There is no guarranty even from the same provider and source that you are getting always the same quality. Already in the studio they may have different quality signals from movie to movie. Even with high tech analysers the guys have problem to identify such problems like you are experiencing. Probably those problems have nothing to do with corel VS.
If the original movie was on film material, their conversion to digital stream will be always different depending on the convertors and the attention of the operators. There are very sophisticated and very expensive systems for conversion ( basically frame by frame and such conversion takes ages) and also very simple methods I saw conversion made by a single camera and the screen where the original film was projected. This will create different streams with different quality. Also the GOP says it is some cheap channel with extreme long GOP. The top channels have GOPs bellow 50. This makes your life difficult with after recording process.
That means in digital world every program can have different parameters and quality and explains also why sometimes you have no problem with postprocessing on other material you will have many.
As the final equipment (TVset, audio systems etc) tries always to show the best possible results and with human eyes or ears you will not see and hear the differences. The short drops are mostly corrected or hidden, for a video editor it is basic problem, usually there is no chance for correction, ie you will edit the material with full of dropouts in any format. The quality depends also on the distribution network. If the network is in perfect conditions you are getting less errors in the signal, if the network is noisy the quality of the streams drops. It can be only in some time window of the day or over satellite depends on the wheater quality. All these factors will change your recordings and dissable an error free recording or editing.

[weaver]

Regarding the commercials I cannot answer your questions - there are so many systems how the operators handle the commercials. It was also one of the reasons why almost in every country of the world the lawmaker introduced different law articles to control somehow the commercial inserts. Today mostly the sound level is heavily regulated and controlled but the video quality is not yet.
There were channels showing historical B&W films while the inserted commercials were in HD quality. You can imagine the challenge for each device in the network chain to handle such streams.
This could be investigated locally with some better analyser. Mostly even the network operator will not be able to answer your questions. On top of that, as already said, the transmitted material quality is not designed for further processing. On some channels it may be even protected ( DRM) what blocks the equipment to record or edit the stream.