Q.How do I save video captured using Philips PCA635VC to an AVI or MOV file?
Any video that has been captured with Philips PCA635VC can be saved as an uncompressed AVI file. Under “FILE” click on “Save As” and then choose AVI format. Currently, MOV (QuickTime) files are not supported directly by the Videogram Creator software. However, you can bring a file captured using Philips PCA635VC into an application such as Adobe Premiere and save it as a QuickTime MOV file.
Q.Can I make a Videogram that will run at 30 frames per second? Do I need 30 fps?
You can capture video using the QuickVideo Transport or the Philips PCA635VC PC camera at 320x240 reso- lution and 30 frames per second. However, these high-resolution, high frame-rate videos become very large files. Due to the size of larger format files, a standard of 160x120 at 15 frames per second has been adopted by most distributors of video on the World Wide Web. Compared to a video at 320x240 and 30 fps, the lower resolution file contains 8 times less data in its uncompressed form.
Although 30 frames per second (and 60 interlaced fields) is the standard for broadcast NTSC video and televi- sion, other frame rates have been successfully used in other mediums. For example, movies shot on film record at 24 frames per second, and in Europe, the PAL and SECAM standards specify 25 frames per second (and 50 fields). The usual compromise between accurate display of full motion video and file size is 15 frames per second.
As communication bandwidth, storage capacity and compression technology advance, the standard for video dis- tribution in electronic form may move to higher resolutions and higher frame rates. For the time being, a higher resolution of 320x240 is more likely the next advance rather than increasing the frame rate above 15 fps. The advantages of the higher resolution probably outweigh the greater motion tracking of an increased frame rate.
Q.What is the real difference between 15 and 30 frames per second? Are there certain applications where 30 fps would be required?
The difference between 15 frames per second (fps) and 30 fps is how much motion will be captured and convey- ed when the video is played back (this affects the apparent smoothness of motion). The file size will also be affected since there will be twice as much data at 30 fps. Most video providers over the web have standardized on 15 fps (some use video captured at even lower frame rates - 8, 10 or 12 fps) recognizing that 15 fps gives a very good representation of motion (as can be seen in the Videograms we have posted on our web site).
We have found that for most applications, 15 fps is sufficient but we recognize that there will be certain situ- ations where 30 fps is required. This may include situations where smooth continuous motion is absolutely nee- ded. That is why the QuickVideo Pro and Philips PCA635VC support 30 fps capture and the Videogram Creator and Player support 30 fps playback. Users should recognize that file sizes will be much larger, and wit- hout an extremely fast computer, performance will be most likely degraded during playback. This degradation during playback can result in dropped frames and even a loss of synchronization (sync) between audio and video. This is often seen as more disturbing to the viewer than a lower frame rate.
Q.How long does it take to compress a file into a Videogram?
Most of the work in creating a Videogram is performed by the host processor. So the time required to create a Videogram will depend on the system CPU speed and the amount of memory (RAM). In some cases, the hard disk performance will also have an impact. Typically, it will take between 3 and 5 times the duration of the actu- al video clip to create a Videogram on a Pentium system running at 90 MHz. The exact time will depend on how much activity is contained in the video clip and the audio and video codec chosen for the compression.
Q.Will a faster system shorten the time required to make a Videogram? Yes. See above.
Q.Will a faster system improve video capture quality?
If the Philips PCA635VC is used in a Pentium 90 system, you should be able to capture video without problems up to 320x240 resolution. When using a slower machine there is the possibility that your system will drop fra- mes during video capture (if the system is not fast enough to transfer the captured data to your hard disk, frames will be dropped from the video stream). The components in the system that will affect whether frames are drop- ped are CPU/system bus speed, amount of system memory, and hard disk performance.
We recommend a 133-MHz Pentium with at least 16 MB of memory and a fast hard disk drive. Hard disk drive performance is measured by data transfer rate and seek time. A larger data cache in the hard disk will not help with a large stream of video data. In general, SCSI hard disks will perform better due to the faster data transfer rates of the SCSI interface. SCSI drives are typically faster in seek times as well. For our own video capture sys-
