"Missing" audio in VPX16

emmrecs wrote on 1/15/2025, 9:50 AM

(The thread title is deliberately cryptic!)

but I wanted to seek the wisdom of fellow-users of this software about a very strange problem!

I recently needed to digitise, for a client, a VHS tape. Following the demise of my computer which included a Canopus ACEDVio PCI card and the fact that the new computer has no PCI slots, I decided to test the Magix, (Black) USB Video Convertor. After several tests using some of the different output options offered by the convertor (initially I tried the .avi user defined option, it produced files recorded at 124mbps(!) but these did not export very well at all to DVD [the intended final output]; I then tried "MPG-DVD" option, c.4kbps, but the quality was rather low, to say the least.) The other options seemed to offer no real "improvement" over this MPG output.

So, being the owner of Topaz Labs Video AI (which I find one of the best softwares for video upscaling) I opened the "MPG-DVD" file in Video AI, chose to have it apply a little enhancement (increasing the bit rate to about 6kbps) and the file successfully exported! The Audio was simply set to "Copy", with no enhancement or changes made to it, officially!

I then opened this "enhanced" version in VPX16, and there was no audio. I opened the same file in my normal "file player", PowerDVD 17, and it played perfectly, video and audio!

I then looked at the Audio data from MediaInfo for both the original and processed files; here is that data:

The "original":

ID : 192 (0xC0)
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 2
Duration : 55 min 36 s
Bit rate mode : Constant
Bit rate : 224 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Frame rate : 41.667 FPS (1152 SPF)
Compression mode : Lossy
Stream size : 89.1 MiB (5%)

The "processed":

ID : 2
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 2
Codec ID : mp4a-6B
Duration : 55 min 36 s
Bit rate mode : Constant
Bit rate : 224 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Compression mode : Lossy
Stream size : 89.1 MiB (4%)
Default : Yes
Alternate group : 1

Obviously, I can see some "different" lines of data; but surely that cannot explain why the file has no audio (and no visible waveform) when opened in VPX16?

I have asked Topaz Labs support about this and they can offer no reason for the behaviour. Before I ask Magix Support I wanted to see whether the collective mind of users in this forum had any ideas to offer?

In the longer term, because I am quite often asked by clients to transcribe VHS video to DVD, I am going to take the plunge and buy an external PCI Expansion Enclosure so I can use my old, but still excellent quality, PCI card for digitising video.

All thoughts very gratefully received!

Jeff

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Comments

AAProds wrote on 1/17/2025, 6:16 PM

@CubeAce

Ray, VPX is correct. Here's the Virtual Dub readout:

CubeAce wrote on 1/17/2025, 7:43 PM

@AAProds

Hi Al.

Now I'm confused. Where has the mov. container format come from?

@Gid

Yes, sorry, I read the colour depth by mistake. Not used to seeing both parameters at once.

Ray.

AAProds wrote on 1/17/2025, 7:59 PM

@CubeAce

Ray, a VDubism. It shows that for all MP4s.

johnebaker wrote on 1/18/2025, 3:11 AM

@emmrecs, @CubeAce, @Gid, @ericlnz, @Reyfox, @AAProds

As I previously commented there is a 'non standard' combination of an AVC video stream with a MP2 audio stream,

From the MP2, standard, AFAICS there is no defined bits/sample, and the encoder uses a "dynamic" bit depth.

On decoding the decoder decides which the bit depth it wants to use, normally 16-bit, however as seen by the different results above, it can vary .

Added: MediaInfo does not show a bit depth per sample for the MP2 audio, however it will show the bit depth per sample when the audio is an encoded format that does have fixed bit depth per sample.

John EB

emmrecs wrote on 1/18/2025, 3:39 AM

@johnebaker @CubeAce @AAProds @ericlnz @Gid @Reyfox

My continuing thanks to you for your research!

I've heard back from Topaz Support this morning who have suggested a "workaround" of converting the audio to AAC whilst processing the original file. I hope to "test" this later today, computer problems permitting, (don't ask!!)

Of course, I have replied to ask whether, therefore, their software should not allow the audio of such source files to be "copied" (I think John's earlier comment about the non-standard combination is the key). I await their response to this!

Jeff

Gid wrote on 1/18/2025, 6:52 AM

I've heard back from Topaz Support this morning who have suggested a "workaround" of converting the audio to AAC whilst processing the original file. I hope to "test" this later today, computer problems permitting, (don't ask!!)

@emmrecs Hi, I didn't mention earlier when I tried ShutterEncoder to Rewrap your file I did also try Rewrap with Convert - AAC chosen, someone else would need to define what exactly this does but to me the video is left alone & only the audio gets converted. The export works no problem in MMS.

I didn't mention this because you are converting at least part of it & that's a workaround not a solution, if that makes sense.

ericlnz wrote on 1/18/2025, 6:44 PM

I did also try Rewrap with Convert - AAC chosen, someone else would need to define what exactly this does but to me the video is left alone & only the audio gets converted

@Gid Yes, that's my experience. It's very useful. I did however run into problems converting Jeff's file's audio to PCM. Windows Media Player doesn't play the audio and VP21 plays it as a screech. Maybe VPX handles it better but I don't have it installed to check.

Gid wrote on 1/18/2025, 8:02 PM

@ericlnz Hmm, no problem with VP22, PCM 16Bit & AAC. I don't know what changes were made since VP21 (315), I have no additional sound card & VP22 is pretty much at default for most of the settings esp the audio.