Stuttering sound

[jparnold]

I have rendered my movie using MPEG sound and when played on my stand alone DVD player (attached to my TV) the sound stutters a bit during TWO particular scenes both of which start with a 'cross fade' from black. I have tried the same DVD on a different stand alone DVD player which while not quite as bad still has a stutter at the same point in the movie.
When I play the rendered (MPEG 2) file (the one used to create the DVD file) on my PC I cannot detect any sound stutter at the same point in the movie.
What could be causing it? All I can think of is perhaps a bad (DVD) burn but if so why doesn't the picture stutter at the same time OR that the stand alone DVD player can't handle the (compressed) data.
Would I be better rendering the movie using LPCM audio output which is not compressed?
Lastly when using cross fade is it best to also mark the audio as 'fade 'in' or should the cross fade automatically do this?

[Trevor Andrew]

Hi John

A little strange that the sound problem does not show on the rendered video prior to burning, I assume that when you burn the video file that it is not rendered again. So what you have within the rendered file is what you should get on the dvd.

Does the poor sound only happen during the transition or does it extend further.

As for the audio / Fade-in/out
The audio is not faded when you apply the Crossfade transition, this only affects the video.
I usually apply ¡¥fade-in/out¡¦ to audio using the same duration as the transition.
Seems to work well.

I usually use DigitalDolby for my audio with no problems

[jparnold]

Trevor,
Thanks for your fast reply.
The stutter (seems to be a single stutter when the sound appears to drop out once only for a split second) only seems to occur either during the cross fade in or immediately after the fade in completes.
When I create a DVD I (Share) CREATE VIDEO FILE which creates the rendered MPEG 2 file and then I (Share) CREATE DISK importing the rendered file(s).
I have never tried DIGITAL DOLBY
Have you seen an article on the merits etc of the different types of sound (compression) for a DVD either in this forum or elsewhere? I seem to remember once reading that some DVD players may have trouble with one or more compressed audio types.
I wondered if my PC is better able to handle highly compressed data than a stand alone DVD player.
I have just noticed information on the different audio formats at http://www.gromkov.com/faq/general/dvd_ ... rmats.html which is interesting but makes no mention of whether or not any stand alone may have trouble with any of those formats so maybe they don't. It DOES though state - (1) AC3 (Dolby Digital) is the best format to use in DVD and (2)Only leave it as PCM if final disc size is unimportant or if unusual distortion occurs from AC3 or MP2 compression.

[Trevor Andrew]

Hi John

The size of Mpeg Audio and Digital Dolby is about the same, using similar bit rates
I leave the bit rate as the default of 256, and 2 channel.

Sorry to say I have heard of these problems in the past (a long time ago, think VS 8 ) with no definite conclusion.
The transition seems to be the culprit and changing to another type may solve the problem.
Saying that the crossfade transition is probably the most stable of all.

John you are using crossfade and not fade to black?

I would assume that the problem exists immediately after rendering, unfortunately playback on the pc may not pick it up. Your tv system probably does a better job of reproducing the sound, faults and all.

By the way what version of VS 9 or 10

I would try using the cross fade transition and the Audio Fade-out and Fade-in, the latter giving an audio x-fade effect. Use the same time duration for each.

[Ken Berry]

If you are not applying fade-out and fade-in over a transition, I am surprised you are not getting more stutters. There is going to always be a drop or noticeable change in sound levels from the audio in one clip to that of the next unless both have an absolutely constant sound source playing in both of them. But the momentary cut in the audio of one clip and the start of the audio in the next clip, to my mind, will always sound distinct, no matter how short, and -- I would have to add -- also sound a bit unprofessional!

As for audio standards, I agree with the source you quoted to the effect that I too use LPCM audio when I am burning video which would not otherwise take up a full DVD. After that, I tend to use AC-3 more out of habit than anything else. But in PAL land, mpeg layer 2 and AC-3 dual channel stereo are much of a muchness in terms of both size and quality. And with my new Canon HV-20 high def camera, I am having to get more used to mpeg-layer 2 since that is apparently the audio format the camera uses.

In fact, you only have to worry slightly about using mpeg layer 2 in NTSC countries since it is not in the international NTSC standard. Many older NTSC stand-alone players, moreover, could not play mpeg layer 2 audio, though most new ones can these days, it seems.

FWIW, I might note that I too used to have a slight blip over transitions using, IIRC, VS9. I tracked it down to the virtual editing that the program used -- or rather, my lack of skill with it perhaps. As you know, you can cut and move clips all up and down the timeline yet the original video remains as is, and the cuts and other edits are only virtual, recorded in the .vsp file until finally rendered. I found that some cuts I had made were not frame perfect, and that I might accidentally have included a frame from a scene I had just cut at the beginning of a virtual clip I was moving elsewhere on the timeline. The result would be a slight jump in the picture around the transition, though the audio blip associated with that orphan frame was not noticeable since I used audio fade-in and out over the transition. But I imagine if you didn't use the fade-in and out, you would also get an audio blip that way.

(The solution I found, by the way, which I have continued using to this day, is to make your cuts but then use 'Save Trimmed Video' for each new trimmed clip. This creates a new and real clip, rather than a virtual one. And since I tended to test them, any extra frame(s) at the beginning was easily detected.)

[jparnold]

Thanks Trevor and Ken,
(Trevor) I think that you may have "hit the nail on the head" with your question about using Fade To Black as I had done so but only in a couple of places (I normally use cross fade (used as follows: video clip - cross fade - black colour - cross fade - video clip). I have replaced the fade to black with cross fade.
Also I had noticed in the past that at times when I used cross fade between adjacent video clips without fading the sound out and in there was often a brief increase in loudness during the cross fade and it stands to reason that this would occur as there was sound on sound which would cause a brief increase in loudness. Could it be that when using sound from one clip over the top of another (during a transition) then the sound output would be too high causing 'clipping' and so distortion?

It's a pity that we can't have a preference setting which allows automatic fade out/fade in of the sound where cross fade is used - maybe one to add to the Wish List, or has it already been entered on the list.

I will keep in mind your (Ken) method of using 'Save trimmed video'. I guess you do this even if you are trimming a short video clips anyway (eg trimming a clip of say 10 seconds to say 4 seconds) - I always capture video with 'detect scene change turned ON'.
Lastly (Ken), once you trim a clip and use 'Save trimmed video' do you use that method in the Timeline and if so does VS then automatically (re)link the trimmed video (in the Timeline) to the new saved trimmed video clip or do you need then to drag it onto the Timeline and remove the existing clip?

I will change check for any other "fade to black" transitions and replace them and also apply fade out/in to the audio when using transitions.

Lastly I have read with interest a few post in past by members using TmpGenc - do either of you know if TmpGenc renders to a noticeable different (better) video quality than VS? One would hope that it does as it is a dedicated rendering program (ie doesn't do anything else). I used to use TmpGenc when I started in video editing as at the time (around 2000 and VS was version 6) I wanted to render to SVCD for better quality than VCD and I didn't have a DVD burner at the time so used TnpGenc to render to SVCD (VS 6 couldn't do SVCD if I remember correctly)

[Ken Berry]

Not sure about your reasoning about a sound amalgamation during a transition. I *could* understand it if you had actually overlapped two clips e.g. by having one in the main track and the other, slightly overlapped, in an overlay track. Then you really would have two different bits of audio overlapping each other. But that is not the case with a cross-fade or any other transition. The clips -- and their audio -- are end to end, not overlapped, so neither are the audio tracks of either overlapped.

As for Save Trimmed Video -- yes, I save all my files, and most of my clips are around the 8 - 10 second mark. It becomes a bit demanding, I recognise, and is probably no longer necessary. But it is just something I have gotten into the habit of doing as second nature... But in fact, while a new icon for the new and real file appears in the Library pane, it is not inserted automatically to update the timeline. It would be nice if it were, but it ain't!! So in fact you have to manually remove the 'virtual' clip from the timeline and manually insert the new, real clip in its place...

[jparnold]

Ken,
I was assuming that when cross fade was applied between two adjacent video clips then even though the video clips are on the same track (NOT one overlapping the other on the overlay track) that when VS renders then the last 1.0 second of the first video clip (assuming a 1 second cross fade) is overlaid on the first 1.0 second of the next video clip even though that is what is seen on timetime eg
----|-----------|
.....|..............| first video clip
----|-----------|
.....|transition|
.....|-----------|---------
.....|..............| second video clip
.....|-----------|---------
Sorry about the example I have forgotten how to embed spaces so used a period (.) to replace a space.
In fact when you apply a transition the the end of the total video on the timeline decreases by 1 second.
The rendering results in the end of the first video clip gradually fading TO. NOTHING and the start of the next clip fading FROM NOTHING.
I was assuming that VS does NOT fade the audio content resulting in DOUBLE the volume during that one second (sound on sound from the two video clips).
I proved this (audio) with a test project placing two small video clips on the timeline with a cross fade transition between them and then selecting the AUDIO VIEW to see what the wave form would look like however VS displays a blank section in the audio view where the transition is.
I did though notice that when I played the timeline the sound contained a COMBINATION of sound from both video clips during the transition with a resulting slight increase in volume)