Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
I am pretty sure that I will encode at 640x480 but don't know about anyother settings or how they will affect file size.For a normal 1-hour show (most of our favorites are this long), what kind of file sizes am I lookingat?This will affect the size of the hard disk I buy for the storage. I doubt that you can see the difference between a 720x480 pixel and a 480x480 pixel recording, so I would recommed go down to 480x480 pixels. That saves 25% of the data. If you want to export to DVD you might however consider 720x480 pixels and keep the recordings in MPEG2. Also if you want to use the output of a PVR-350 you should keep the recordings in MPEG2. In all other cases you can let MythTV transcode to MPEG4. The encoding rate is very much up your personal taste. If your signal is bad you need a higher data rate. I usually record 480x576 pixels (PAL) at 4.5 Mbits/s in MPEG2 and transcode it to 1.4 Mbits/s in MPEG4. On some channels I can see the artifacts, on others I can't (except in special situations like fast scrolling text). Shows that I want on DVD are recorded at 720x576 pixels at 4.5 Mbits/s in MPEG2. ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
I doubt that you can see the difference between a 720x480 pixel and a 480x480 pixel recording, so I would recommed go down to 480x480 pixels. That saves 25% of the data. If you want to export to DVD you might however consider 720x480 pixels and keep the recordings in MPEG2. Also if you want to use the output of a PVR-350 you should keep the recordings in MPEG2. In all other cases you can let MythTV transcode to MPEG4. The encoding rate is very much up your personal taste. If your signal is bad you need a higher data rate. I usually record 480x576 pixels (PAL) at 4.5 Mbits/s in MPEG2 and transcode it to 1.4 Mbits/s in MPEG4. On some channels I can see the artifacts, on others I can't (except in special situations like fast scrolling text). Shows that I want on DVD are recorded at 720x576 pixels at 4.5 Mbits/s in MPEG2. Thanks for the insight. If I just keep it as MPEG2, what kind of file size should I expect? I'm imagining about a gigabyte per hour. Is that high, low, other? ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
On 9/20/05, Tony McDowell [EMAIL PROTECTED] wrote: snip Thanks for the insight. If I just keep it as MPEG2, what kind of file size should I expect? I'm imagining about a gigabyte per hour. Is that high, low, other? I'm not sure of my settings, but with a PVR-250 (mpeg2) I'm recording at 2.5 gigabytes/hour. I believe the average is ~2 to 2.2 GB/hr. Josh ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
Thanks for the insight. If I just keep it as MPEG2, what kind of file size should I expect? I'm imagining about a gigabyte per hour. Is that high, low, other? That really depends on your bitrate and how clean your signal is. I get about 2.3 to 2.6 Gig an hour. If I lower it to only get around a gig it looks horrible. ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
On 9/20/05, Tony McDowell [EMAIL PROTECTED] wrote: the main purpose of our machine is for recording / encoding video for playback *only* on our TV, what are some good encoding settings? I am pretty sure that I will encode at 640x480 but don't know about any other settings or how they will affect file size. For a normal 1-hour show (most of our favorites are this long), what kind of file sizes am I looking at? This will affect the size of the hard disk I buy for the storage. First off, you can never have enough hard disk space, and sooner or later a hard drive is going to fail and you're going to wish that you had RAID. Okay, so... If you stick with 720x480 and the stock settings in mythtv and a PVR-X50 card, you're probably going to burn about 2.1GB PER HOUR for recordings. I tuned the recording settings down so that my shows take just under 1gb per 30 minute show. This makes it easy to fit more content onto DVDs for me. I set my settings for mythtranscode to be somewhat aggressive, I bump resolution down, I bump audio rate down, and have decreased the min/max bitrate settings. This lets me transcode shows I don't want to burn to DVD, or want to watch later and store them while only taking about 900MB PER HOUR. Most of the time, I can't tell any difference. I'm away from my system, so I can't give any more specific info, but that should help you get started with planning. You should start with default values and adjust them *SLIGHTLY* (probably down), test and repeat until you find the best settings for you. I would plan on buying a 400gb drive if you're going to store all of your recordings on that drive. -Ross ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
On Tue, Sep 20, 2005 at 02:31:36PM -0500, Tony McDowell wrote: I doubt that you can see the difference between a 720x480 pixel and a 480x480 pixel recording, so I would recommed go down to 480x480 pixels. That saves 25% of the data. If you want to export to DVD you might however consider 720x480 pixels and keep the recordings in MPEG2. Also if you want to use the output of a PVR-350 you should keep the recordings in MPEG2. In all other cases you can let MythTV transcode to MPEG4. The encoding rate is very much up your personal taste. If your signal is bad you need a higher data rate. I usually record 480x576 pixels (PAL) at 4.5 Mbits/s in MPEG2 and transcode it to 1.4 Mbits/s in MPEG4. On some channels I can see the artifacts, on others I can't (except in special situations like fast scrolling text). Shows that I want on DVD are recorded at 720x576 pixels at 4.5 Mbits/s in MPEG2. Thanks for the insight. If I just keep it as MPEG2, what kind of file size should I expect? I'm imagining about a gigabyte per hour. Is that high, low, other? FWIW, 1GB/hr is Tivo's Basic Quality setting. Their Best Quality setting is about 3GB/hr. --Rob signature.asc Description: Digital signature ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
When resizing, is it possible to accidentally stretch the image? I saw someone say 480x480 wouldn't be a noticeable difference from 720x480... is the because of the way a TV uses scan lines? On a monitor it seems like it would be very different. I'm curious because I want to transcode HDTV (1920x1080, 1280x720, and 850x480) down to 850x480. For HDTV pulled off of QAM/Cable, I'm seeing MPEG2 file sizes of about 6.2 GB/hr. ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
On Tue, Sep 20, 2005 at 12:44:03PM -0700, Ross Campbell wrote: I set my settings for mythtranscode to be somewhat aggressive, I bump resolution down, I bump audio rate down, and have decreased the min/max bitrate settings. This lets me transcode shows I don't want to burn to DVD, or want to watch later and store them while only taking about 900MB PER HOUR. Most of the time, I can't tell any difference. I'm away from my system, so I can't give any more specific info, but that should help you get started with planning. You should start with default values and adjust them *SLIGHTLY* (probably down), test and repeat until you find the best settings for you. Any chance you might post your settings when you get closer to your system? 1G/hour is about where I'd like to end up and having an example of settings that produce results in that range would be useful. -- The freedoms that we enjoy presently are the most important victories of the White Hats over the past several millennia, and it is vitally important that we don't give them up now, only because we are frightened. - Eolake Stobblehouse (http://stobblehouse.com/text/battle.html) ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
On Tue, 2005-09-20 at 15:58 -0400, Brian McEntire wrote: When resizing, is it possible to accidentally stretch the image? I saw someone say 480x480 wouldn't be a noticeable difference from 720x480... is the because of the way a TV uses scan lines? On a monitor it seems like it would be very different. To be fair there are two issues here. First of all you have the immediate source of the signal. In general they will be 1) Pure analog 2) Some form of mpeg compression If you have dish network afaik they encode normal channels with 480x480 mpeg 2 compression. In general this will limit the frequency content in the signal so that it is not useful to sample it at a higher resolution than 480x480 again. Of course with the case of the number of lines, that is a fixed quantity and you simple sample at 480 lines and be done with it. In the case of the horizontal resolution this is not 100% true since, unfortunately, you can't sample the exact same positions as were originally encoded, and there is always the case of noise being added due to the digital to analog conversion. (The noise may increase the frequency content of the signal, and thus require a higher sampling frequency to preserve the information content. Of course, it is quite possible the capture card will filter out high frequency noise before capturing data anyway.) In the case of a typical myth setup, you will likely see some black bars on the side of your encodings meaning your capture card is possibly sampling parts of the tv signal that has no data and dish network never encoding anything into, so that to, be paranoid, and assure you are not losing quality you might have to sample at a bit more than 480 pixels horizontally. Perhaps 512x480 or 640x480 for instance. Of course things are not that simple either. As you increase the sampling resolution, you must also increase the bit rate of the encoding to avoid degradation. This is why a 480x480 encoding may look better than a 640x480 encoding if the bit rates are the same. If in doubt, try various settings and compare them. There are a lot of factors here, and the vague arguments I made only make a case for not going too much beyond what the signal was originally encoded as. In the case of a pure analog signal that was received by an aerial, things are different and it may indeed help to go 720x480 or 640x480, provided you also give the codec a large enough datarate to handle the video. Finally, if you absolutely know you are going to transcode something anyway, you generally want to have the capture size set to whatever your final size will be, and set the initial capture datarate a bit on the high side so you preserve as much quality as possible prior to the final transcoding to mpeg4 or whatever. I used to use huffyuv for captures in windows, even though it used a very high datarate, because I wanted the initial encoding to be lossless, before I edited the system and converted it to mpeg. (Huffyuv is probably too high of data rate for myth and useless with cards designed to capture in mpeg2 anyway since you would have to add a pointless recompression.) I'm curious because I want to transcode HDTV (1920x1080, 1280x720, and 850x480) down to 850x480. For HDTV pulled off of QAM/Cable, I'm seeing MPEG2 file sizes of about 6.2 GB/hr. ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
On 9/20/2005 12:37 PM Josh Burks wrote: On 9/20/05, Tony McDowell [EMAIL PROTECTED] wrote: snip Thanks for the insight. If I just keep it as MPEG2, what kind of file size should I expect? I'm imagining about a gigabyte per hour. Is that high, low, other? I'm not sure of my settings, but with a PVR-250 (mpeg2) I'm recording at 2.5 gigabytes/hour. I believe the average is ~2 to 2.2 GB/hr. I use a PVR-250 with 480x480 and this is my rate. Drew -- Visit The Alchemist's Warehouse Magic Tricks, DVDs, Videos, Books, More! http://www.alchemistswarehouse.com ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
Others have done a good job of talking about higher end, so let me talk about the lower end. I have Dish network coming in through an anlog line, into my tuner, and out to a 20 regular TV. So my source resolution is lowish, but my line is very clean, and my output device isn't very picky. :) My defualt setting is 480x480, 2000Kbps (the only thing I changed in the MPEG2 profile was bitrate, nothing else). This gets me just under 1 gig per hour, and if I sit 6 feet away, there's really no perceptible degradation. My high quality is 544x480, 3500Mbps (1.8 gig/hr). Live TV is 640x480, 4500Kbps. I've also got a Matrox Marvel G400. I have to capture at 352x480, because 720x480 will bog down my system. Quality is still just fine, comparable to the PVR-250, although the file size can be about 10 gig/hr (I transcode these to about 1800Kbps). If I had a bigger, fancier TV, I might be more picky. Earlier, before I sorted out my coaxial cable problems, I had some noise on the line, and it did really bad things to the picture quality. --- Tony McDowell [EMAIL PROTECTED] wrote: i'm buying some of the parts I will need for the MythTV box in the next few days. Our rig will use a primary hard disk for actually running the OS on and a secondary hard disk that will be exclusively for storing data on. Since the main purpose of our machine is for recording / encoding video for playback *only* on our TV, what are some good encoding settings? I am pretty sure that I will encode at 640x480 but don't know about any other settings or how they will affect file size. For a normal 1-hour show (most of our favorites are this long), what kind of file sizes am I looking at? This will affect the size of the hard disk I buy for the storage. I'm not expecting folks to just hand out information here, but a good site for tutorials on this topic where I can research it myself would be greatly appreciated since I know little about how MythTV encodes and the official How-To was a bit slim on this topic. thanks! .tony ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Re: [mythtv-users] Tutorial on Encoding (mostly re: file sizes)
Dave Sherohman wrote: On Tue, Sep 20, 2005 at 12:44:03PM -0700, Ross Campbell wrote: I set my settings for mythtranscode to be somewhat aggressive, I bump resolution down, I bump audio rate down, and have decreased the min/max bitrate settings. This lets me transcode shows I don't want to burn to DVD, or want to watch later and store them while only taking about 900MB PER HOUR. Most of the time, I can't tell any difference. I'm away from my system, so I can't give any more specific info, but that should help you get started with planning. You should start with default values and adjust them *SLIGHTLY* (probably down), test and repeat until you find the best settings for you. Any chance you might post your settings when you get closer to your system? 1G/hour is about where I'd like to end up and having an example of settings that produce results in that range would be useful. Not transcoding settings, but probably still useful... http://mythtv.info/moin.cgi/UserManual_2fTechnicalDetailsAppendix_2fRecordingParameters Mike ___ mythtv-users mailing list mythtv-users@mythtv.org http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
