On Tue, Feb 24, 2004 at 08:49:20PM -0800, Douglas Fraser wrote: > Setting up a system with two dc10+ cards, one for capture and the other for > playback. I was hoping someone could give me a tip on how to configure > lavrec & lavplay to access the different cards.
For lavrec, you set LAV_VIDEO_DEV, LAV_AUDIO_DEV and LAV_MIXER_DEV as appropriate, and for lavplay, you set LAV_VIDEO_DEV and LAV_AUDIO_DEV as appropriate. > The system will be in consent record while letting the user > playback any of the captured segments without shutting off the > lavrec function. You are trying to recreate TiVo pause live TV functionality, right? If so, this isn't going to quite work like you want. Until lavrec closes out a segment and moves on to a new segment (and you will need to use the %d segment filename syntax) you will be unable to view that segment. In other words, lavplay/lav2yuv will refuse to read the beginning of a file that lavrec is still recording into because the .avi or .qt (quicktime) header has not yet been set up. Only once lavrec closes out that segment and starts a new segment does the file header get setup and then lavplay/lav2yuv see the file as a playable .avi or .qt file. You can however make the segments small, look for the --max-file-size parameter, to minimize the impact of this little known fact. The movtar file format is capable of simultaneous recording and playback into a single file, but it's not been maintained for a long while and for me at least it was buggy and did not work to make a usable recording. Also keep in mind that you are going to need a disk I/O subsystem that is capable of keeping up with the load you are about to put it to. A single dc10+ recording a full size (for a dc10+) frame of 640x480 at a quality setting of 75 with the new dc10+ driver will dump right about 7.5MB (mega bytes) per second to disk. Going to a quality setting of 100 will dump right about 10MB/sec. Therefore, at these settings, for simultaneous playback, you need to be able to handle writing 7.5MB/sec to 10MB/sec while also being able to simultaneously read 7.5MB/sec to 10MB/sec back from disk. That's not an impossible rate to sustain on modern disk hardware, but it's also something you need to keep in mind when setting the system up. Also, writing of data to disk is very timing critical, lavrec has only a small internal buffer to hold recorded frames and sampled audio before writing them to disk. If the disk write rate falls below that average value for just a bit too long, lavrec's internal audio ring buffer will overflow, at which point it will abort recording and exit with an error message. > I've seen the LAV_VIDEO_DEV env variable, but I'm unsure how to set > it to two different cards. You set it to the video device you want to use at that time, e.g., (if using bash): export LAV_VIDEO_DEV=/dev/video0 lavrec ... > I came across the -zrdev option in MPlayer, does anything like that > exist in lavtools? Yes, but it's the three environment variables instead of being command line options. ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
