On Mon, Sep 05, 2005 at 02:00:42PM -0400, Brian McEntire wrote: > I have an EDTV that doesn't go to full HDTV specs. It can display > 480p, 720p, and 1080i formats, but it's native resolution is 852x420 > so any of the other formats are going to be downsampled. > > I'm having success recording HDTV over ATSC OTA with MythTV, but > playback is choppy and I know it is because my computer is currently > underpowered. I could upgrade, and probably will, but in the mean > time, and even after I upgrade, there is no reason to have HDTV > shows at higher than 480p since they need to be downsampled to > display on my TV anyway. > > Can I save disk space and possibly improve playback performance with > transcoding? How to I manually and automatically set shows recorded > in 1080i or 720p to be transcoded down to 480p?
I have a similar setup as you (record HDTV OTA for display on my "HDTV" with only 856x480 resolution). Using the internal myth transcoder (mythtranscode): In the setup menus, enter the "Recording Profiles", "Transcoders" and set up the target resolution to be whatever you want it to be (e.g., 852x420) and some bitrate (I use 4400kbps with the bitrate scaled against a 640x480 resolution, to end up with about 2GiB/hr) for the "High Quality", "Medium Quality", and "Low Quality" transcoders. There are no predefined defaults; you have to set them up yourself. In the "Default" recording profile, enable the "auto-transcode" checkbox. This checkbox is for mixed systems where one might want to auto-transcode recordings captured from an HD-3000 (say), but not re-encode recordings captured from a PVR-x50 card that has hardware-assist. Then in your recording schedules, enable auto-transcoding for that recording schedule. Other people use nuvexport and "user jobs", but this requires more configuration. I think the trade-off is that mythtranscode is optimized for speed over quality, while nuvexport takes longer but produces higher-quality results for a given target filesize. But I don't use nuvexport so I can't say from my personal experience. --Rob
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