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.avi File Shows 4.29 Gb For Dvd But 7.49 Gb When Dvd-Dl Chosen

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I realize I should be clearer... I've got an .avi movie file that is 701MB in size. When I drag the file to Toast 10 Pro's DVD Video window the target file size shows as 4.29 GB when I have DVD selected as the target media. When I switch to DVD-DL as the target media the file size on disc shows as 7.49 GB.

 

I've moved a few other .avi files of different sizes from different sources with similar results.

 

I've deleted plist and prefs files and nothing changed.

 

 

Help!

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What your seeing here, in my opinion, is that Toast's Automatic encoding setting tries to make full use of the available space, to maximize quality by setting average bitrate so that nearly the whole disc is used. It's not a bug; it's a feature.

 

Note that using almost twice the bitrate (disc space) doesn't necessarily mean twice as good. Beyond a certain point it is very hard to see any improvement visually.

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What your seeing here, in my opinion, is that Toast's Automatic encoding setting tries to make full use of the available space, to maximize quality by setting average bitrate so that nearly the whole disc is used. It's not a bug; it's a feature.

 

Note that using almost twice the bitrate (disc space) doesn't necessarily mean twice as good. Beyond a certain point it is very hard to see any improvement visually.

 

 

That makes a lot of sense. Now if the file inside the .avi container is an MP4 and by creating a DVD in the DVD-Video pane of Toast I'm creating an Mpeg2 file (I think) when it creates the Video_TS folder does it make sense to bump up the bit rate at all? Or should I just make the bitrate low enough to match the file size of the original .avi file?

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That makes a lot of sense. Now if the file inside the .avi container is an MP4 and by creating a DVD in the DVD-Video pane of Toast I'm creating an Mpeg2 file (I think) when it creates the Video_TS folder does it make sense to bump up the bit rate at all? Or should I just make the bitrate low enough to match the file size of the original .avi file?

Just choose the Automatic setting at the quality you want and trust Toast to make a good choice about bit rate. The number at the bottom of the window is pretty much irrelevant because the actual size isn't known until Toast finishes the encoding. It's generally good to fit about 2 hours of video on a single-layer DVD although Toast will fit more than 3 hours at greater compression. Personally, at three hours I prefer to use DL media.

 

Since you're starting with an .avi file it may be wise to install the perian codec (www.perian.org) if you haven't already done so. Otherwise your DVD may be lacking any audio depending on the codec that was used for the audio in the .avi.

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Just choose the Automatic setting at the quality you want and trust Toast to make a good choice about bit rate. The number at the bottom of the window is pretty much irrelevant because the actual size isn't known until Toast finishes the encoding. It's generally good to fit about 2 hours of video on a single-layer DVD although Toast will fit more than 3 hours at greater compression. Personally, at three hours I prefer to use DL media.

 

Since you're starting with an .avi file it may be wise to install the perian codec (www.perian.org) if you haven't already done so. Otherwise your DVD may be lacking any audio depending on the codec that was used for the audio in the .avi.

 

 

 

How do I know whether Perian is already in my system or not? What files do I look for, and where?

 

Trusting Toast is cool, but how do I trust and verify what is actually happening. It seems to me that using over 7GB on a DL disc when the source file is less than 800Mb is a waste unless it absolutely needed.

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If you have Perian installed it will appear in the "Other" section of System Preferences. The easiest thing to do is just download and install it even if it is already there. There is no way the file from your movie will become anything close to 7 GB unless it is about four hours long. If you want to see how big the final DVD actually will be choose Save As Disc Image rather than clicking the burn button. Then look at the size of the resulting .toast file. The disc image can be burned to video DVD using the Image File setting in the Toast Copy window.

 

Another thing to note: when Toast does the MPEG 2 encoding it writes the video and audio files in the Roxio Converted Items folder in your Documents folder. When the encoding is done Toast multiplexes the two together (invisibly) and authors the VIDEO_TS folder. When you quit Toast the converted items folder is emptied unless you change that in Toast preferences.

 

I haven't studied this but based on what you've posted it seems to me that the scale at the bottom of the Toast window is referring to the space available on the disc rather than the size that the video will be after encoding.

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Tsantee,

 

Thanks for the input.... I have to go to work right now but I will double check what actually happens first thing tomorrow... I remember that toast actually burned a file to a DL DVD that was much much bigger than it had to be, almost the full disc. I tossed that disc but your idea of writing an image file is less wasteful for an experiment. The colored slider at the bottom of the page went from empty to almost full when I dragged the video file into Toast. I thought it was REAL freaky that the final file size was almost the full disc capacity in BOTH the single and double layer scenarios using the same 701 Mb file.

 

I'll post back once I test some more......

 

Pete D.

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The file size of the source file should NOT be a guide for the file size of the output file, as they use different video codecs. MPEG-2 needs a higher bitrate than MPEG-4, all other parameters being equal.

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Tsantee,

 

Thanks for the input.... I have to go to work right now but I will double check what actually happens first thing tomorrow... I remember that toast actually burned a file to a DL DVD that was much much bigger than it had to be, almost the full disc. I tossed that disc but your idea of writing an image file is less wasteful for an experiment. The colored slider at the bottom of the page went from empty to almost full when I dragged the video file into Toast. I thought it was REAL freaky that the final file size was almost the full disc capacity in BOTH the single and double layer scenarios using the same 701 Mb file.

 

I'll post back once I test some more......

 

Pete D.

I just took a look at that scale and see that it is supposed to be giving an estimate of the final size, so I was wrong in my previous post about that. As I mentioned, you'll have a very good quality video DVD on a single-layer disc if you keep it around 2-to-2-1/2 hours in length. Don't worry about file size. Think about total amount of video in time on a disc. Toast will fit over 3 hours to a single-layer disc but the quality begins to suffer when it gets that long. I believe Toast will ask if you want to make a single-layer or dual-layer sized disc image.

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OK! Once more with feeling. The original file size of the file I'm experimenting with now is 1.44gb - when I drag it to Toast's DVD-Video screen I get a file size of 4.20gb on the bottom scale. When I change the selection to DVD-DL the file size becomes 6.05gb. When I select BD or BD-DL the file size remains 6.05gb.

 

The movie length is 1 hour and 44 minutes, so the 2-hour time concern does not apply here. I am concerned about conserving storage and I am trying to get multiple movies onto a DVD-DL disc without compromising the quality of the video.

 

How do I find out the actual mechanics of what is going on here? I'd like to make an educated decision regarding trusting Toast versus knowing what the compromises are of taking matters into my own hands by customizing the parameters of the file until the file is a more reasonable size in toast.

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OK! Once more with feeling. The original file size of the file I'm experimenting with now is 1.44gb - when I drag it to Toast's DVD-Video screen I get a file size of 4.20gb on the bottom scale. When I change the selection to DVD-DL the file size becomes 6.05gb. When I select BD or BD-DL the file size remains 6.05gb.

 

The movie length is 1 hour and 44 minutes, so the 2-hour time concern does not apply here. I am concerned about conserving storage and I am trying to get multiple movies onto a DVD-DL disc without compromising the quality of the video.

 

How do I find out the actual mechanics of what is going on here? I'd like to make an educated decision regarding trusting Toast versus knowing what the compromises are of taking matters into my own hands by customizing the parameters of the file until the file is a more reasonable size in toast.

The data size of your source video is irrelevant. What Toast is trying to do is give you the highest-quality video for the disc media you are using by setting the greatest average bit rate that will fit the disc and still not exceed the maximum specifications for a video DVD. So on a DL disc Toast can use a higher bit rate (taking up more space) than it can for a single-layer disc. However, it cannot fill the DL disc because that would require a bit-rate exceeding what's allowed for use on DVD players.

 

While you might presume that the maximum bit rate will produce the highest quality that isn't always the case. Very high bit rates can cause playback problems such as stuttering because it is more work for the DVD player to decode. Generally an average bit rate near 6 mbps will yield a picture looking essentially as good as one near 8 mbps. When you go below the 6 mbps average you may start to notice drop off in quality when compared to the same video encoded at a higher rate. However, you might not notice without that comparison.

 

If you don't want Toast calculating a bit rate that will come close to filling the DVD you can set your own bit rates in the custom encoder settings window. For example, if you set the average bit rate at 4.5 Mbps and the maximum at 6 Mbps my sense is you'll still have avery good looking video DVD that will be smaller than what Toast automatically creates for a single-layer disc. You can also reduce the audio bit rate to squeeze the space down a little more although I like Toast's default of 192 kbps. Turn on half-pel to improve encoding quality of action sequences.

 

When you are done creating your custom settings choose Save as Disc Image so Toast encodes the video. When it is done mount the disc image and preview the video at actual size using DVD Player. You can experiment with different settings to see how those affect file size and picture quality. Since Toast uses variable bit rate encoding in which higher bit rates are used for scenes that have a lot of changes in their content and lower bit rates in scenes that have little change in content it is impossible to determine in advance how big a file will be for any specific video. Some videos of the same length will be smaller in file size (videos of paint drying) than others (videos of NASCAR races). I once found a freeware application called Mr. Bitvice that helped in estimating what average bit rates are needed to fit a certain length of video onto a certain size of disc. Unfortunately that application doesn't work in recent Mac OS versions.

 

If you are wanting to fit two movies on one DL disc then it is best to add them both to Toast, choose automatic and have Toast encode them for dual-layer DVD. You'll get close to the maximum bit rate that will fit that much content (in hours and minutes) to the disc which also will be the best quality that Toast can do for that amount of content. Otherwise you'll need to encode them separately at your custom settings until you get them both the right size to fit onto a DL disc (which, unfortunately, isn't twice the size of a single-layer disc).

 

You probably feel I'm giving you a run around. You're wanting a straight answer about which setting to use to get the best result. You don't like that Toast is giving you different sizes when you tell it you want it to fit a single layer disc than when you tell it you want it to fit a DL disc. I'm saying don't worry about it. Add your two videos and make the DL disc using the automatic setting. If you are unhappy with the results then you can't have them both on one disc because the quality is being too affected by the level of compression. In that case you'll need to use two discs. But for videos of less than 2 hours in length I think you'll find the quality to be very acceptable with one movie on a single-layer disc and two movies on a DL disc.

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