Audio clipping, could it be the software or old source? How to find out

[TKH]

Folks:

Appreciate your time reading my query.

I have an 2009 iMac (dual core processor but with loaded RAM - 16 GIG - and SSD startup OS drive and 2 TB main drive). Not the latest, but not so slow it should cause issues. I run it clean and maintain it well.

I'm using iMovie 11 in import videos from my Sony DCR-TVR19. Tapes are 10 years old. When I get a 60 min. tape imported and start to edit the crap and make a home movie, I notice much of the higher frequencies--when their level is too high--gets "clipped" or simply digitized and sounds bad. It's almost as if the software can't interpret the message and it cuts it and phony(ies) it with some digital crud.

Could this be happening with iMovie? That is doesn't know what to do with less than ideal data? Or could this be tapes have aged and the digital message is somewhat lost? This happens even if the video is solid and flowing--meaning not just when video cuts out. Clearly signal loss. One concern is if video is still intact, the data is there...then why would audio clip at higher frequencies?

I'm thinking of trying a different import tool other than iMovie to see if there is a compression issue or something. I don't really know how iMovie imports and if it automatically compresses Mini-DV signals upon import.

By the way, I could upload a segment to youtube if folks felt they needed to hear the effect to understand. Please advise.

Any suggestions or advise would be appreciated.

TKH

[smrpix]

That camera can switch between 12 bit and 16 bit sound and may have both analog and digital soundtracks (I can't tell from the manual.) There are menus to access all those settings, try playing with those and see if there's a better version lurking in there somewhere.

A 2009 mac will probably only run versions of iMovie that still handled DV -- which is what you want.

[TKH]

Ok, so here is a clip I imported from mini-dv to [removed youtube, actual file below in later post] This is about 15 seconds. Be warned, loud kids; not idea audio setting. That said, we shouldn't have the clipping even if the pitches of the kids being loud. Clearly it's not the video I'm worried about; this video was shot with night vision on the 4th of July; however, the audio is clearly struggling.


I also did a "get info" on the source and it reads:

Format: DV/dvcpro-ntsc, 720X480 (64 lineal pcm, 16 bit little-endian sign...)

FPS: 29.97
Data Rate: 30.822 Mbit/s

[Cornucopia]

The Mac is likely not doing anything. It could be misinterpreting the data (doubtful, though).

Check the recording IN THE CAMERA (using headphones) first...does it "clip" there?
What is the audio set to: 12bit/32kHz or 16bit/44.1kHz or 16bit/48kHz?
If the first one, 12 bit is low enough bitdepth to allow you to hear the "grunge" distortion caused by quantization error. Also, 32kHz sampling means the top freq. is ~15-16kHz. This is well within the range of hearing of most people, middle-aged or less, without hearing loss. So it would sound more "muffled/clipped" than the 44.1 or 48k rates, though not by a lot.

If you're going to upload - do it HERE, not on youtube, where it will get further (and greatly) degraded. Capture & save a ~5-10sec clip. At 25Mbps, that should be ~15MB-30MB, well within this site's filesize limits.
At the very least, post a text readout of the detailed MediaInfo info.

I assume you are transferring properly: via Firewire DV transfer. If not (like using USB), then that could very well be your problem.
The way iMovie is SUPPOSED to work with DV cameras is this:
Camera -> DV/Firewire/IEEE1394 port -> Firewire cable -> Mac's Firewire port -> iMovie.
Digital DV data stream (muxed video+audio+aux data) streams out and in and is captured/saved by iMovie without change (usually left as Type1, raw *.DV or *.DIF file stream).

Scott

<edit>another thing to check is: Is the clipping analog or digital? If analog, it probably got there via the microphone preamp in the cam.</edit>

[newpball]

What happened around 5.5k?

[TKH]

Scott: Ok, I've uploaded it to the web site. So no youtube changes. I am using Firewire cable to my macs firewire port, so no USB.

Check the recording IN THE CAMERA (using headphones) first...does it "clip" there?
Yup. There is minor detected clipping, but not NEARLY as bad. I wonder if its just age of the tape or age of the camera....not sure how to tell other than buying a new camera and hoping it doesn't have the issue. Not sure I can even get a new mini-DV camera these days.

What is the audio set to: 12bit/32kHz or 16bit/44.1kHz or 16bit/48kHz?
Unfortunately, that's not an option in the menus. Lame.

At the very least, post a text readout of the detailed MediaInfo info.

Original Media/2005-07-04 20_40_23.mov
Size: 66.8 MB
Format: QuickTime/MPEG-4/Motion JPEG 2000 format
Stream count: 3
Duration: 00:00:18
Bit rate: 31033 kb/s
Meta info:
compatible_brands: qt
minor_version: 0
creation_time: 2015-02-17 18:00:49
major_brand: qt

Stream 0
Type: video
Codec: dvvideo
FourCC: dvc
Duration: 00:00:18
Width: 720
Height: 480
Sample aspect ratio: 8:9
Display aspect ratio: 4:3
Pixel format: yuv411p
Frame rate: 29.98 fps
Bit rate: 28771 kb/s
Meta info:
handler_name: Core Media Data Handler
creation_time: 2015-02-17 18:00:49
language: und

Stream 1
Type: audio
Codec: pcm_s16le
FourCC: lpcm
Duration: 00:00:18
Bit rate: 2048 kb/s
Sample rate: 32000 Hz
Sample format: s16
Channel: 4
Meta info:
handler_name: Core Media Data Handler
creation_time: 2015-02-17 18:00:49
language: und

Stream 2
Type: data
Meta info:
language: und
timecode: 00:00:43;06
creation_time: 2015-02-17 18:00:49
handler_name: Core Media Data Handler

Oh, I am using one of these. I don't think this should be causing any issues:

http://www.cable-warehouse.co.nz/Firewire%20800%20To%20400%20Adapter%20Converter

Its on the end of my firewire cable from my camera that plugs into my iMac.

[newpball]

The youtube video and the download is not the same.

[TKH]

The youtube video and the download is not the same.

Fixed and removed. I've since attached the actual video here. Live and learn.....

[Cornucopia]

Well, it could be that the file is fine but the decode by iMovie/CoreAudio is at fault. I notice that CoreAudio is telling MediaInfo that the audio stream is 32kHz/16bit - that is not possible. There is no such thing as DV 32/16, just 32/12 or 44/16 or 48/16. If CoreAudio treats your 32k/12 as 16bit, it could be padding the extra 4bits incorrectly (possibly reading the next 4bits?). If it's misrepresenting 44or48/16 as 32/16, that's even worse.

Do you have the facility to do a test capture (via Firewire) to a PC?

BTW, you did NOT give us an upload of the original, just a mp4 converted file, which is not helpful in getting to the root of the problem.

Yes, those adapters can be (and have been known to be) a problem. Do you have ANY footage ever shot with these cams and captured with this method and this device/Mac that does NOT exhibit audio distortion?

Scott

[TKH]

Scott: I uploaded a clipped version using MPEG Streamclip, so its still in .mov. Hope that helps. To your questions. I don't have a PC to do such a test. I've noticed on 10 converted 60 min videos (all 10 year old tapes) they all have the audio clip. I chalked it up to old tapes but then started to think there's got to be more going on here.

As for the cable, my Mac has Firewire 800; i suppose I need to find a cable that runs on the mac (800) but also the small imput on the camera (9pin/4pin). I doubt that will do it but I might as well try. Worth the $10 bucks for such a cable.

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Well, it could be that the file is fine but the decode by iMovie/CoreAudio is at fault. I notice that CoreAudio is telling MediaInfo that the audio stream is 32kHz/16bit - that is not possible. There is no such thing as DV 32/16, just 32/12 or 44/16 or 48/16. If CoreAudio treats your 32k/12 as 16bit, it could be padding the extra 4bits incorrectly (possibly reading the next 4bits?). If it's misrepresenting 44or48/16 as 32/16, that's even worse.
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As for your comment about bit conversion above, how would I ever go about addressing that? I can't imagine the cable converter is causing the software to wrongfully encode it, but I honestly don't know, thus I'm hear asking for help.