Auto Recompression

[RobertH]

OK here is the scenario:

Setup:
SS using a PVR250 card in mpeg mode with auto transcode to wmv mode

Whats going on:
1) A job just finished recording the auto transcode starts immediately
2) Another job begins to record while the transcode is occuring
3) because of bandwith of writing mpeg stream from pvr to disk and cpu overhead from reading from same disk the recording that is occuring gets hiccups in the stream or there is an increase in artifacts because of the disk thruput.

This scenerio presents two options:
1) force the transcoder to only perform at a certain time frame
2) force the transcoder to transcode into another folder (preferably on another disk drive)

so with that out of the way does anyone know how to accomplish the second option??? or will I have to wait and hope for them to add it as a feature of the next version...............................

[CO_Coding_Cub]

You know, on my end I'd say the issue is that the transcode pegs the CPU at 100%. I personally wish SS would give us a proc usage setting, if I could set transcodes to use 25% proc, I'd be happy. I hate that I have to set transcodes for overnight if I want to use the computer at all...

I also use a PVR-250. I don't think the hiccups are because of HDD bandwidth, I think it's the SS decoder engine. On my box (AMD Athlon 1800+) SS requires ~80% proc to playback a PVR-250 MPEG-2... WinDVD (and WMP using the same decoder) requires 25-30%. I have no issues watching recordings in WMP while SS is recording. I do have issues if it's transcoding (very jumpy playback.

The devs have said that they are working to resolve the playback issues and have implied that it will be in the next "point release"

[RobertH]

My other problem is that half the time the deinterlacer for conversion doesnt work very well. Most of the time it can keep up with the video and you dont see blurring or the "lines" but for any action or where there is noise in the mpeg stream the deinterlacer doesnt work at all. Why didnt they implement a deinterlacer in the mpeg drivers like the WMV drivers have??

[PBMax]

Are the issues with the recording in Live TV or in the actual recorded file?

You can set a transcoding time by going to the Video Recompression and Edit Contranints. The default is 1AM to 7 AM.

You can edit the properties of a show to transcode to a separate store. This setting was omited in the Video Recompression settings. This has been bugged.

The Video Recompression algorithm is set to use all the idle processor time to recompress the video. Meaning that even though the processor is pegged if you needed CPU time for other tasked PVS would give it to you.

[CO_Coding_Cub]

PBM....

I have transcodes set for 4AM-6:30AM (that's the only block of time I'm not recoding in consistantly. Last night I was watching an ep of Stargate in WMP. 4:00 hits and the video started getting a bit stuttery, something along the lines of a 1/4 second freeze every 4 seconds. This is still tollerable for watching, but I'd much rather be able to set TC to use at most 50% proc and NOT use the time constraints. The most power I've ever seen my box use has been during playback and it's about 35% (this is a dedicated TiVo-replacement computer). As it stands, my recompression window is just big enuf, if I add another file (like the occational Auto Race for my roommate) I get a backlog because I don't have a better time slot to dedicate to transcodes. A proc usage setting would be damn helpful.

I might point out that I don't use SS for playback because it draws about 70% proc for MPEG-2 files, while WMP using the WinDVD decoder uses 30-35%. I use my TV's tuner for Live TV (tho this is VERRRRY rare in my house).

... I just noticed that my proc usage estimates have changed from my earlier post Ah the fun effects of alcohol (I just turned 21 Monday) *grin* .... Note to self, veg in front of TV, not computer, when drinking....

[PBMax]

I don't think this is a CPU issue.

I think the stuttery problem is caused by the hard drive. I got the same thing when I was Recording a shows, watching another show, and copying files to another computer. All three drive activities happening on the same drive. I don't think the drive was fast enough.

Do you have a separate drive that you can try to transcode the files to? This may solve the drive access problem.

[CO_Coding_Cub]

Originally posted by PBMax
Do you have a separate drive that you can try to transcode the files to? This may solve the drive access problem.

My setup won't let me test that way (2 discs setup as dynamic volumes, my recording volume spans both discs).

Whatever the issue is here, I just think a "background transcode" option would be kewl. If I could set my transcodes that usually take ~35 min to take 2-3 hours, I'm fine with that. I'd like that solution better than the "window" at night, since my recordings are fairly evenly spaced across the day.

[PBMax]

I entered this as a feature request.

[RobertH]

CO_Coding_Cub , i know the dynamic spanned volume thing looks nice but this adds a lot of overhead to the drive access and for things like doing mpeg realtime it may overwhelm the system that windows uses to do the partitioning and file system allocation. I used dynamic spanned volume on one of my previous setups with 7krpm drives and the recordings would fall off if there was any other access do the drive or controller the drives were on. I dont think the spanned volumes were designed for speed in mind i think they were for archive type applications or something. Also if any drive in the spanned set dies (i know this first hand) ALL data on the entire spanned set is LOST as i have yet to find a partition/file system tool to recover data off of dyn volumes

[CO_Coding_Cub]

RH, I understand the possible loss of data, but considering this is a dedicated machine, all I'd loose is the system and recordings... I can deal with that. As for Dynamic volumes and performance, aside from the auto-transcodes, I havn't had a single performance issue. I have nearly constant recordings from 3PM till 3AM, and users watching shows or listening to music from 8PM til anywhere round 4AM. I _DO_ have performance issues if I watch shows thru SS, but I've found I like myHTPC much better for this. I've found that WinDVD runs at nearly half the proc useage as SS does with DI turned off, and WinDVD is running DI anytime it's needed automatically.

Besides, it's my understanding that the dunamic volumes is at least loosely based off RAID (it's essentially software-managed RAID). If they preserved anything from RAID, I'd assume that it would give slightly better drive performance than using singly-dedicated disks. RAID will write the data to the least busy (most responsive) disk available. Considering that most of the recording volume fills the 160GB drive, I would think most of the data gets written there first, since the other chunk is shared with the system volume. Just my thoughts, don't know for sure what the comp's doing. All I know is the only time I have playback issues is during a transcode, I've never had any recording issues.