imovie vcd export produces pops and clicks in audio!

[kgreene]

I'm having a problem with the imovie vcd export...the audio has pops and clicks. I am using quicktime 5, I think the newest imove (2.0.3?) and toast 5 and os 9.1.

The original does not have this problem, and the vcd export function using quicktime player does not have this problem.

any ideas?

[Koz]

I have 'pops' and 'clicks' as well in most of my exports from iMovie 2.0.3 to VideoCD using Toast 5 Titanium. (OS 9.1, quicktime 5.0.1, and on different machine OS 9.1 quicktime 4.1.2)

They are NOT frequent, NOT regular, and I'm going nutz trying to figure this one out. I review the scenes in iMovie, and there are no pops in the audio. There does not seem to be any correlation to scene change, volume change or any fluctuation that might account for extraneous noise.

I made a 2minute VCD export of a still frame to see if random pops are present in all exports... (if it were a product of the multiplexing) nope, perfect silence in the mpg.

In iMovie, I lowered the volume level (of the clip in the "time line mode" to 60% 50% and even 40% of full, and when I export to VCD again, the volume is lower, but the pops and clicks are in the SAME EXACT PLACE. Sometimes in the middle of someone speaking, sometimes in a zero-noise pause... It is puzzling and annoying.

I'll echo kgreene.. any ideas?

[kgreene]

The only thing I can think of trying is downgrading the components. I am using quicktime 5 pro..are you using pro? Have you tried downgrading components. I made vcds for a while before noticing this problem, so I am wondering if this is due to upgrading...possibly from 9.0.4 to 9.1? Have you upgraded to 9.2.1? Also, perhaps quicktime 4 instead of 5 pro or quicktime 5 instead of 5 pro...oh wait, you tried different quicktime versions already. I guess the only other thing is older versions of imovie. Have you tried it on a g3 vs a g4? (Maybe there is some altivec code that has a problem? Then again, the video CD export takes so long I don't think there IS any altivec code in it.)

The most irritating thing is that I COULD export the entire imovie as uncompressed DV and then encode it with quicktime player with the video cd codec. This does NOT produce the pops, but quicktime player will not compensate for the nonsquare DV pixels and I don't get the correct video output!

Have you tried contacting roxio tech support? Someone on their mailing list has the same problems and said they contacted roxio and other places and couldn't get it resolved.

Kevin

[Koz]

In testing out all ways to export from iMovie, I adjusted the volume to 0 (zero, nothing) in the "time line mode" and discovered something very interesting.

For any footage I grabbed off the air or via my VCR, then digitized with my Digital8camcorder, I export to VideoCD, and there ARE pops and clicks.

The footage I took with the camera, edit in iMovie, then export to VideoCD, has NO pops and clicks.

ergo (unless Im missing something) Something in broadcast signals creates the pops and clicks. perhaps closed captioning signals? In all broadcast stuff I see a thin band of unusual signals at the very top of the image... those are always cropped by a television, but perhaps they have something to do with it.

can anyone else confirm that the pops n clicks only happen with non-camera footage?

Koz

[kgreene]

hmmm....I believe that that top line is closed caption information, but I think I have pops and clicks from something where I don't see that line, but it IS from a tv broadcast. (That show must not have closed captioning.)

I have discovered that you can export a full quality DV file from imovie but set the ratio to 640x480 instead of the default 720x480. This will allow you to use quicktime player to open the file and export to video cd without the pops and clicks. This is at least a workaround, if not an irritating one. Let me know if this works for you.

Kevin

[Koz]

I upgraded to Quicktime 5.0.2, and nothing new, still pops and clicks for VideoCD export from iMovie 2.0.3

Roxio tech support knows of the problem and they say it is an Apple Quicktime issue, not anything wrong with Toast Titanium... I expect when I talk to Apple they will say nothing is wrong with Quicktime, but is a Toast Plug-in issue. (reminds me of Ford vs Firestone)

Has anyone tried exporting VideoCDs from iMovie for OS X?

HINT: to easily hear if pops n clicks are present, uncheck all three audio tracks in the timeline mode of iMovie, then export.

[kgreene]

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On 2001-09-03 13:41:44, Koz wrote:
Roxio tech support knows of the problem and they say it is an Apple Quicktime issue, not anything wrong with Toast Titanium... I expect when I talk to Apple they will say nothing is wrong with Quicktime, but is a Toast Plug-in issue. (reminds me of Ford vs Firestone)
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Have you tried exporting the imovie to 640x480 dv (29.97 fps, no compression on audio 48khz) and then exported from quicktime player to video cd with that dv file? This should be using the SAME video CD export code that the imovie plugin calls. This does NOT produce clicks. Point this out to roxio.

This means that the problem lies either in the toast imovie VCD plugin (since the vcd quicktime plugin from them works fine from quicktime player) OR it is imovie itself (or the way it or its plugins interact with quicktime.) However, if its own plugins export fine then that would imply a problem with the toast plugin.

Kevin

[desertracer]

I have the same problem in my iMac with Toast 5 Ti and iMovie 2. I'ved tried almost everything and I found a way to solve it. I disable almost all of the extensions except the quicktime related and some system extensions. The problem is gone now. I don't have time to find out which extension(s) cause the problem (we have a new-born last week). Hope this help.

[Koz]

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On 2001-09-04 07:45:09, kgreene wrote:

Have you tried exporting the imovie to 640x480 dv (29.97 fps, no compression on audio 48khz) and then exported from quicktime player to video cd with that dv file? This should be using the SAME video CD export code that the imovie plugin calls. This does NOT produce clicks.
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OK, back after many weeks and dozens if not hundreds of testing sessions, and have interesting results with a one-time-resize solution that also solves the audio problem.

Short version:
A) bad news: Don't export to 640x480 then use Quicktime Pro to convert to Toast VideoCD mpg format; by resizing the entire movie twice, it causes a loss of sharpness, lessens color saturation, and there is a problem with a stuttering 'repeated frame' per second. (more later in 'details')

B) good news: Open raw "DV" files in the iMovie2 "Media" folder using Quicktime Pro, export right back to DV Stream with a new name. Work on project in iMovie2 as normal using the QuicktimePro exported files. When exporting final project to Toast VideoCD format, NO pops and clicks. The new DV streams look identical to the originals, and as far as I understand the codecs, opening a DV stream and exporting to a DV stream is a lossless operation. (Please correct me if this is not correct)

It will add another step (one that takes approx 2X real time to perform) so now it will take 20X original time instead of 18X (your Mac mileage will vary), but the video mpg output is beautiful, and the audio is click n pop free.

Does anyone know of a Macintosh video capture utility (other than iMovie2) that saves video directly to a DV stream? Perhaps those DV streams wouldn't need to be resaved for this to work. I have Premiere LE and ReelEyes, but although they can capture DV video, they save to a Quicktime Movie using DV compression, NOT a raw DV stream.

Koz

OK, now the details on 'stuttering' repeated frame whenever one exports from Quicktime Pro to Toast VideoCD format:

When I exported from iMovie2 to 640x480, 27.97fps, and then used Quicktime Pro to export to Toast VideoCD format, I noticed something odd. My test video just happened to have a moving line of text at the bottom, and I noticed the mpg was 'stuttering' for an instant, once a second. (the 640x480 did NOT stutter.) After many tests with a variety of sources, I discovered that EVERY export from QuicktimePro to "Toast VideoCD" mpg format had this stutter, it just was MUCH less noticable when there wasnt a precisely-moving object in the source. If you use the arrow keys to advance frame by frame, you'll see that once every 30 frames it will show the same frame, even tho this does NOT happen on the original source.

If you want to verify this:
Use iMovie2 to import some live video of the news or stockmarket watch with a smoothly scrolling text at bottom, use iMovie2 to export directly to Toast VideoCD format. Play mpg encoded movie with Quicktime player and it is Perfectly smooth.

Then Export that same iMovie2 clip to Quicktime, 640x480 29.97fps (using any or no compression), then use QuicktimePro to export to Toast VideoCD format. Play mpg encoded movie with Quicktime player and it has a slight stutter once per second.

AND, even if you just open the raw iMovie2 DV stream file with QuicktimePro, then export to Toast VideoCD format, (using any choice; fit, crop, or fit&crop) the stutter is there. (as well as being wider than tall, but this was just to test to see if the middle step caused the stutter, which it doesnt)

I have not done any tests yet on dragging QT movies into Toast to see what those results would be. I ran out of steam after "testfile219.mpg".

[jack01]

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On 2001-10-05 01:11:20, Koz wrote:
OK, back after many weeks and dozens if not hundreds of testing sessions, and have interesting results with a one-time-resize solution that also solves the audio problem.
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Both the audio and video problems you're experiencing are caused by the root of all multimedia evils: low-precision fixed-point math! Unfortunately, QT (designed back in the late 80's) uses fixed-point math almost everywhere. Add a couple bad design decisions in the Sound Manager, and this is what happens.

On the audio side, the problem is that the VCD export requires sample-rate conversion from 48kHz (DV) to 44.1kHz (VCD MPEG-1) prior to encoding. The Toast plugin asks the Sound Manager for 44.1kHz data, the Sound Manager notices the input is 48kHz and does the conversion on the fly. The problem is that sample-rate conversion is not a trivial task, it requires a fairly complex DSP filter to be done right. One side effect is that if you split a sound stream into chunks like the Sound Manager does, then sample-rate convert the chunks independently, you're going to end up with two potential sources of clicks:

1. Alignment clicks, unless the chunk size is the least common multiplier of 44100 and 48000 (7056000 or 147 seconds of sound.)

2. Filter-related clicks, because when the DSP filter is applied to chunks, it does not produce matched output chunks (the last sample in the first chunk doesn't match the first sample in the second chunk.)

The way to avoid both kinds of clicks is to use a windowing tecnique, ie. effectively crossfading each chunk into the next. The Sound Manager seems to do this to avoid problem 2. (otherwise the output would sound a lot worse!) but does not buffer effectively enough to avoid problem 1. (more specifically, because all the buffer size calculations are made using integer ratios and fixed-point math.)

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When I exported from iMovie2 to 640x480, 27.97fps, and then used Quicktime Pro to export to Toast VideoCD format, I noticed something odd. My test video just happened to have a moving line of text at the bottom, and I noticed the mpg was 'stuttering' for an instant, once a second. (the 640x480 did NOT stutter.) After many tests with a variety of sources, I discovered that EVERY export from QuicktimePro to "Toast VideoCD" mpg format had this stutter, it just was MUCH less noticable when there wasnt a precisely-moving object in the source. If you use the arrow keys to advance frame by frame, you'll see that once every 30 frames it will show the same frame, even tho this does NOT happen on the original source.
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The video problem is also related to fixed-point math! The problem here is that "29.97 fps" isn't really 29.97 frames per second, but rather 30000/1001 frames per second which comes out to 29.97002997... Unfortunately QT uses a fixed-point number to represent frames per second (and more generally all timestamps,) in a binary representation that cannot quite come close to the exact value. To make the problem worse, every QT component deals with the lack of precision in different ways, so depending on which input and output component you choose, you'll get different symptoms of the same problem. The repeated frame you're witnessing is probably matched by a disappearing frame somewhere else, since otherwise you would lose audio-video sync in only a few seconds. Instead, you typically won't run into sync problems until a movie has been running for hours, and even then of only a couple frames.