MovieShop is a tool that processes QuickTime movies into a format that plays well from CD-ROM. This program uses many different methods in order to tune the movie for a constant flow of data. Big spikes of data, such as multiple key frames in a row, can cause your movie to play badly as well as stop playing altogether.
Data rate -- the amount of data required at any one moment to play a movie.
Data rate is specified in K/Sec, this means kilobytes per second. The higher the number, the faster the decompressor and the device supplying the data have to be. A peak data rate from the current generation of CD-ROM drives is 150 K/Sec, the new generation arriving has a data rate of 300 K/Sec.
Playing at this peak data rate does not leave time for the other parts of playing a movie, such as:
a) Decompressing the video data. b) Copying the video data to the screen.
c) Playing the sound. d) Control overhead for next frames.
e) Seeking to the data. f) Starting a new track going.
The two areas that impact playing a Movie the most are reading the data from the drive (including seeking) and decompressing that data. Experiments have shown that using Apple's Video compressor, Apple's SC CD-ROM drive, and the Mac LC, that the data rate acceptable is 90K/Sec to 95K/Sec. If your Movie will only be played from Hard Disk then you can more than double this data rate. If you will only be playing on higher end CPUs then you can also increase it. If you have a custom decompressor that is faster than the one specified here then you could also increase the data rate.
The new Apple Compact Video decompressor in QuickTime 1.5 is faster than normal. Because of this you can use a data rate of 100 K/Sec, instead of 90 K/Sec, when that compressor is selected.
Movies -
A simple Movie will contain a Video track and a sound track. These two tracks are played synchronously by QuickTime to create the Movie. The video track is fed through a video decompressor and then the resultant image is displayed on the screen. The sound track is fed through the sound chip in the computer and played out either your computer's speaker or the output audio jacks.
A more complex movie may contain many video and sound tracks, caused by editing movies. QuickTime will play these many different tracks at the appropriate time to make the movie play smoothly. Because there can be a great deal of overhead in ending one track and starting another track, the overhead to do this may have an impact on the Movie (it depends on how far apart the edits are).
Edits -
Edits also cause the data in a Movie to be out of order for normal playing. QuickTime will jump around in the Movie to get the appropriate data whenever the current time in the Movie is. If jumping around in a file is done then there is a "seeking" time penalty that you will pay. If the Movie has a very low data rate and/or the "seeking" time is very short (like on a Hard drive), then it will not affect playing of the Movie. However, if the data rate of the movie is very high and/or the "seeking" time is very long (as on a CD-ROM drive), then it will seriously impact playing the movie.
Flattening -
"Flattening" or making a "self contained" movie will place the data in a new movie in "close to" the optimal order. The data rate of the Movie may still exceed the capabilities of a CD-ROM drive and the Movie will not play properly. If the data is slightly out of order, not optimal, then the lowest level of QuickTime (the famous Data Handler) will do some fancy footwork and help play the movie the best possible.
"Flattening" or making a "self contained" movie does not do any recompression to keep the data rate below a maximum value. This type of Movie may exceed the data rate of the playback device, like a CDROM player.
Movieshop's purpose -
What MovieShop does is to take all the video tracks and make them into one video track. It does this by "playing" the input movie in an off screen buffer and then compressing the result into one video track. Doing this, many video tracks can be merged into one video track, at the cost of doing a recompress. When this is done all the Text tracks are disabled. This prevents the text from being converted from text strings into image data.
It takes all the sound tracks and makes them into one sound track (at the same sample rate if you choose). Sound tracks are not yet merged together. MovieShop will currently locate whichever sound track that is at that corresponding movie time and use the sound data from that track. So if you have multiple sound tracks that are not overlapping then the result will be a merged sound track. If you have multiple overlapping sound tracks then you will loose some of the sounds in the output movie.
MovieShop lays out the sound and the video data in an optimal way for QuickTime, to eliminate any drive seeking. It makes all necessary adjustments to keep the data rate at or below the maximum value that the CD-ROM drive on a low end computer can handle.
Main MovieShop window -
If you use the default Preference settings, or you have tuned the Preferences to your own settings, then you can use this window to do all the processing.
Bringing in a source movie:
?The "Import..." button is used to bring in the source movie, the movie that is to be processed. You will be presented with the standard file dialog that allows you to select a movie.
An alternate method is to use the "Import..." menu item. Both of these methods accomplish the same thing.
This is the standard file dialog that you select the source movie with.
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We have selected the ever popular "baking a cake" from the QuickTime CD-ROM.
We now have a movie in the "Import", source, area.
The next step is to set the data rate that we want, this is in the Methods preference dialog:
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To run from CD-ROM on the lower speed machines, and using the lower end CD-ROM players, a data rate from 90K/Sec to 100K/Sec is acceptable. If you are making one to run from Hard Disk then set it as high as 300K/Sec. If you do not want any decrease in quality then set it to 900K/Sec and no quality should be lost.
Now we can start the processing, by pressing the "Make the movie" button and giving a destination name and location.
As the processing starts we are presented with a progress window that tells us a lot as it proceeds:
The source name as well as the destination name are both shown. The estimated time left for processing as well as the estimated final size are both displayed and continually updated.
The progress bar reflects where we are while doing the entire movie. This bar will fill in to the right, as the movie is processed.
The top main bar contains a moving graph of the current data rate achieved.
The next bar contains marks for each video frame done and each sound chunk written out. The sound data is a different color from the video data. The height of each video mark is related to its size.
The bar containing "tick" marks corresponds to Video Key Frames, and tracks the other bars.
The next bar is for messages describing the processing currently happening.
Frame is the current video frame working on.
Data rate is the current data rate as the processing occurs. This number changes as processing occurs.
Sim is the similarity value for that frame. This value will vary from 1 to 255. This will read "Key" for key video frames. Similarity is a measure of how close this video frame is to the last video frame processed.
Q is the current spatial quality setting being used.
M is the current motion, temporal, quality setting being used.
Frame Rate sampling
To resample a movie, use this menu selection.
The "Movies natural rate" will keep the sampling rate that the original movie was at, it will not resample the movie at another rate.
"Resample at xxx" will resample the movie at the desired sample rate. These selections are ideal for resampling a movie that was originally captured at a very high sample rate. It is also very useful for something like resampling a movie down from 15fps to 10fps.
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Preferences
This is the preferences dialog that lets you determine how the movie is compressed and processed.
Compression quality can be set using the "Video Settings..." button:
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The left column is for spatial quality settings, while the right column is for motion or temporal quality settings.
The "Min Frame" setting is the lowest quality, on a scale of 1 to 1023, that step #8 will use. The "Min Sequence" setting is the lowest quality that the "Recompress from last Key Frame" items will use.
Choose the desired compressor with the "Compression" popup selection.
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This selection changes the method used for compression. With this unchecked, the comparison during compression is:
a) Previous buffer contains the Input Raw Movie at Time minus 1 step.
b) Current buffer contains the Input Raw Movie at Time.
With this checked, the comparison during compression is:
a) Previous buffer contains the compressed Movie at Time minus 1 step.
b) Current buffer contains the Input Raw Movie at Time.
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Sound can either be left at the sample rate that it is in the original. It can be resampled at 22kHz or 11kHz.
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This setting is for the default data rate setting. The main window will have this number in it the next time this program is started up.
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Pressing this button will bring up the Cropping and Resizing dialog.
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The Key frame spacing is set here. Key frames are those frames spaced periodically in a movie to keep the quality of the movie up.
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What Key frames affect:
a) Larger values.
1) Less Key Frames
2) Lower the data rate.
3) Harder to random access.
b) Smaller values.
1) More Key Frames
2) Higher the data rate.
3) Easier to random access.
Apple Compact Video compressor.
The Apple Compact Video compressor is an "intelligent" compressor. Built in to it are methods to reduce the data rate while maintaining quality.
For this compressor only, the other compressors are not "intelligent" in this way, you should turn off all the methods in MovieShop.
One reason for the data rate control being moved into the compressor is for speed. This compressor is much slower than most other compressors. Using MovieShop methods, a number of retries at compression using different quality settings would be done to achieve the desired data rate.
Since this compressor is very slow, it has the added intelligence to make the best guess at the final quality settings necessary to give the best image quality while still maintaining the desired data rate. So, instead of having MovieShop reduce the data rate by recompressing at lower quality settings, this compressor will pick the right quality settings and do one or more compressions.
The "Sound" menu list is for slight ajustments to your sound before processing it.
There are four (4) menu selections for sound adjustments. The fist two are to aid in "lip syncing" sound to the video. The other two are for slight adjustments to sound speed for VERY long movies. An hour long movie may have sound synced properly for the first 1/3 of the movie and for the last 1/3 it is out of sync. Adjusting the sample rate for the whole movie can adjust this sampling error out. :
a) Shift earlier (Cmd-, or Cmd <, or <, or ,) - This will shift all the sound in the movie earlier in time by 1/30th of a second. Selecting this item again will move it another 1/30th of a second earlier in time.
NOTE: All sound that is shifted earlier in time than the start of the movie will be clipped off. So, if the sound started at movie time zero and then you shift it earlier by 1/30th of a second. All the sound that was from time zero to time 1/30th sec will be clipped off, the rest of the sound will be shifted over to start at movie time zero.
b) Shift later (Cmd-. or Cmd >, or >, or .) - This will shift all the sound in the movie later in time by 1/30th of a second. Selecting this item again will move it another 1/30th of a second later in time.
NOTE: All sound that is shifted later in time than the end of the movie will be clipped off. So, if the sound started at movie time zero and then you shift it later by 1/30th of a second. All the sound that was from the end of the movie minus 1/30th of a second to the end of the movie will be clipped off, the rest of the sound will be shifted over to start at movie time zero plus the new offset.
c) Shrink (Cmd-[ (by 2) or [ (by 1)) - This will scale all the sound in the movie to be shorter by 1/30th of a second. Selecting this item again will shrink it another 1/30th of a second. So if the movie was 39min24sec12/30sec then a shrink will change the sound to be 39min24sec11/30sec.
d) Lengthen (Cmd-](by 2) or ] (by 1)) - This will scale all the sound in the movie to be longer by 1/30th of a second. Selecting this item again will lengthen it another 1/30th of a second. So if the movie was 39min24sec12/30sec then a shrink will change the sound to be 39min24sec13/30sec.
These menus are enabled when the input movie window is selected.
Loading a new input movie will zero out these settings.
