From: "O.T. Byrd" <[EMAIL PROTECTED]> Subject: The Osprey-100, AVI File sizes, and Premiere. I noticed a few questions regarding the Osprey-100, the "AVI 2 Gig limit", etc. and thought perhaps the following would be helpful. First, just a little confirmation about what the Osprey-100 is/is not. Then, on to the AVI file size thing. The Osprey-100 is designed to be a video capture device. This means it will function with any VFW (Video For Windows) application. Whether the application is designed for simple capture, live streaming, capture and later edit, or for video conferencing, the Osprey-100 captures raw, uncompressed video and "hands" it to the application for streaming, compression, editing, or other manipulation. This is always handled by the application and not by the capture device. DirectShow can be used, as well, but is not considered the Osprey-100's "native format". Now, about AVI file sizes. LIMITATIONS: First, when creating any type of file, one should be aware that there is a limitation in Windows95/98 of 2 gigabytes (GB) that limits files (regardless of file type) to the same maximum file size as the FAT16 file system, which is 2 GB minus 1 byte (FAT16 on NT limit is 4 gigabytes). Therefore, on computers using the FAT32 file system, the maximum file size is 4 GB minus 2 bytes. To create larger than 4GB files load NTFS on your NT machine. The file size limitation is hundreds of GB. (232 clusters so file size depends on cluster size setup on disk.) Here are the limits for FAT16: file 2 gigabytes, partition 2 gigabytes FAT16 (NT): file 4 gigabytes, partition 4 gigabytes FAT32: file 4 gigabytes, partition 2 terrabytes NTFS: file 2 terrabytes, partition 16 exabytes (18.4 x 10^18 bytes) Hardware limits: IDE drive size limit: 540 megabytes EIDE drive size limit: 136.9 gigabytes BIOS boot partition size limit: 7.8 GB It should also be noted that: 1. FAT16 partition larger than 2 gigabytes under NT is not visible to MS-DOS 2. NTFS file size limit is actually 2^32 clusters. Current industry standard hard disk sector size is 512 bytes, giving a 2 terrabyte file size limit. AVI FILE SIZES AND THE 2 GB LIMIT: With respect to AVI files, the OpenDML committee has developed a spec for AVI 2.0 files. This includes unlimited file size, interleaved indexes, and support for field indexes in addition to frame indexes. The AVI 2.0 spec was also designed to be backwards compatible. So many applications which do not support AVI 2.0 should still be able to play back the first 1 GB of the file. Beyond 1 GB, additional data is appended with a FourCC chunk code of 'AVIX'. To check if an AVI file is 2.0, run the riffwalk utility provided in the DirectShow SDK and check for a 'odml' format tag. If it exists, the file is AVI 2.0 format. AVI 2.0 is not supported by VFW (Video For Windows), which creates an AVI file in the 1.0 format. The AVI 1.0 format does not support unlimited file sizes and limits one to a 4 GB file size (theoretically). However, due to a bug in the MS api used to create AVI files, the index and a couple other entries are corrupt if you create a file larger than 2 GB. Also, some older players will only play back a 1 gig file. So the following guidelines apply: 1. If you want every app to be compatible with the AVI file, limit the size to 1 gig - if you're only interested in newer apps, limit the size to 2 gig. 2. Vidcap is based on VFW (AVI 1.0) and will create AVI files greater than 2 gig, but the file may appear invalid or damaged to some AVI players/applications since the indexes are corrupt and can't be played back with any player. If Vidcap runs out of space while capturing, the entire AVI file is marked corrupt. 3. You can use the riffwalk.exe utility in the DirectShow SDK to verify an AVI file. It will echo an error if the file is corrupt. 4. To create an AVI file in the 2.0 format one must use a DirectShow application. AVI FILE SIZES AND ADOBE PREMIERE: In our testing it seems that Adobe is Video For Windows based and requires AVI 1.0 file format. This would explain why even file sizes smaller than 2 GB created by a DirectShow application would not be recognized by Adobe Premiere. You may want to visit the following link to Adobe's FAQ site which discusses AVI file limits and workarounds. http://www.adobe.com/support/techdocs/100d2.htm Please check out the new RealForum Bulletin Board at http://realforum.real.com/cgi-bin/realforum/wwwthreads.pl ******************************************************* The RealForum is an email discussion group focused on using RealNetworks products. The RealForum is a place to post messages about the best methods for creating content using RealNetworks technologies and the planning and implementation of streaming-media web sites. 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