Best bang for buck when compressing my Tivo dumps?

[mtcabral]

Hello, relative newbie here. Here's my scenario:

My Best Quality TiVo files (dumped out via DirectShow) leave me with mpeg2 files at 480x480, 29.97, 5800 kbps, coming in at a hefty 2.5 GB each. I'm trying to figure out the best way to compress these. Using guiffmpeg, I can get DVD, SVCD, VCD or MPEG4. Looking for advice on what will get me the most bang for my buck, maintaing quality versus file size? Which format and what resolution and bitrate?

Thanks!
Mke

[TBoneit]

If your DVD player will do SVCD on DVD then Just running software that will check for large GOPS and fix them unless your DVD player doesn't care is the best way. Avoid encoding if you can.

I'd waste a DVD in testing and use DVD patcher to patch to DVD res, add to TDA, Unpatch to 480 by 480 again and author. Test play and see what happens.

I recall seeing that some DVD recorders use a 480 by 480. Pioneer 531/532/533/633 uses 480 by 480 for mn9,mn10,mn11 recording in VR mode. 544 by 480 for other MN settings.

I know I can play 544 by 480 and 480 by 480 in my Sony changers if authored as a standard DVD via the DVD patcher method

[redwudz]

What do you plan to play them on? They appear to be SVCD format and the bitrate is not that high. Any reduction will lose quality, possibly a lot, if you are using the MPEG-2 format and reduce the bitrate to say, half of what it is presently.

If you want to reduce the size much further and still retain some quality, and you don't need them to work with a regular DVD settop player, try re-encoding them to Divx or Xvid. I use VirtualDub Mod for that. With the Xvid codec, you can set the target quantizer to about '2' to give you about the same quality, but at a smaller size. For that, select the Xvid codec in VDM, then click the 'Target bitrate' and it will change to 'Target Quantizer'. Change the number to about '2' and see how it works. If you need smaller filesizes, then it gets more complex. You can do 2 pass encoding at lower bitrates. I would try a 5-10 minute representative clip and encode that with different settings and see how it looks.

BTW, the most important parameter for encoding is the runtime of the video, not the present size. You can plug that into a bitrate calculator and see what your bitrate options are for the size you intend the final video to be. For MPEG-2, bitrates below about 3000 will result in low quality video, in most cases. There are options, but you would have to tell us what you want to do with the video. Bitrate calculators are available in 'Tools' to the left.

And welcome to our forums.

[FulciLives]

Based on things that I have read ...

The TIVO files are MPEG-2 but are at a resolution that is not standard for the NTSC DVD format. So when you re-encode them you need to change the resolution to one that is a standard for the NTSC DVD format.

You can use 720x480 (or even 704x480 but I prefer to use 720x480) which means a slight resize UP or you can do a slight resize DOWN to 352x480.

Now if you resize to 720x480 (also called Full D1 resolution) then you do not really gain any resolution but you don't loose any resolution either.

Now if you resize to 352x480 (also called Half D1 resolution) then you do loose some resolution but it really isn't going to be all that noticeable (knock on wood).

So the best BANG for your buck would be to resize to 352x480 when re-encoding. Also since the resolution here is lower (than if you use 720x480) you can get away with using a lower video bitrate and yet still get great image quality. If you instead go with 720x480 then you will need more bitrate to handle the extra resolution (720 width needs more bitrate than 352 width to look the same or "as good") but again when you upsize to 720 you still are only getting 480 in effect but it will look "sharper" than if you go with a width of 352.

So with most stuff you probably should go 352x480 but with stuff that you really "care about" I would resize to 720x480 instead.

As for the bitrate ... if using Half D1 resolution (352x480) then 5000kbps is the MAX bitrate you would want to use but if you are doing a 2-pass or multi-pass VBR re-encode then you can use an average as low as 3000kbps (with say a MAX of 5000kbps and a MIN of 1000kbps) and still get very good quality (knock on wood).

If you go with Full D1 resolution (720x480) then if you want the image to look as good as the original (in terms of minimizing MPEG compression artifacts) then you would want to probably use a much higher bitrate which will result in a filesize that is as big (if not bigger) than the original file ... but at least it will be 100% DVD compliant unlike the original.

Going Half D1 resolution gives you the benefit of getting a much smaller file size with image quality that is almost as good as the original but you do loose some resolution (although knock on wood not enough in my opinion to make a major drop in quality).

Hope that makes sense

- John "FulciLives" Coleman

P.S.
As other people have indicated there is a way to burn those TIVO files to a DVD Video disc without re-encoding them but since 480x480 is not a standard DVD resolution this trick will create a non-compliant DVD Video disc that will work in some players ... maybe even "a lot" of players ... but surely not "all" players.

[TBoneit]

Tis true they won't be in DVD spec at 480 by 480 OTOH I suspect all the cheapo players could handle them. Some of the name brands would be the problem units. I have sony changers that can do a good job of playing 544 by 480 even with long gops. And if I patch SVCDs to auithor the same way they'll happily play them off of a authored DVD too. But feed it a 640 by 480 sone the same way and end up with a white bar on one side.

I'm suspecting it maight be because the decoder chips are general purpose and can handle the more common DVB resolutions too, I could also be wrong. I figure it is worth a try as all it will cost is a inexpensive DVD. And even if at some point in time in teh future it needs to be encoded to standard then the OP will most likely have a faster computer and they'll be untouched as to quality and be a good placd to work from then.

[mtcabral]

Hi, All,

Thanks for all the quick and terrific replies! I'll read and digest them to my newbie brain later tonight.

In terms of what I'm after here, it's really pretty simple. I want to maintain or nearly maintain the quality of my original recordings, without being stuck with files that are too big. For example, I've noticed that folks often get 45 minutes of video down to about 350MB as avi. I've downloaded some of the these and they look great -- granted, the original source is typically DVD or HD.

So, best case, I wind up with pretty small files that I can pile onto a single DVD and play them back at decent quality. I have the Phillips DVP642/37, which plays just about every format. With the stuff I've been downloading, I can just dump the avi's to the DVD as plain old avi files, and hey play fine. At ~350 MB per sample, I can get 12-13 of them on a single DVD-R

Thanks again!
Mike

[FulciLives]

You are of course talking about XviD or DivX when you say AVI ... but there is a BIG problem here with that format.

It really only works well with a progressive video source and when it comes to NTSC I am talking a 23.976fps progressive video source ... not 29.970fps progressive.

But guess what? ...

All that TIVO stuff is going to be 29.970fps interlaced.

Some of that can be made 23.976fps progressive but that is very tricky to do "just right" and even then some of the TIVO stuff will have to be deinterlaced to a 29.970fps progressive video file.

So the whole DivX/XviD thing is really a very poor choice here.

- John "FulciLives" Coleman

[jagabo]

I agree with FulciLives but... MPEG4 (Divx, Xvid) does support interlaced encoding. And if I remember correctly, the Philips DVP-642 will playback interlaced MPEG4 correctly if it is bottom field first and if you leave it at the full 480 scanlines tall.

Leaving it as MPEG2 is probably your best bet. If you don't need pretty menus and chapter stops burn the MPEG2 files onto ISO data DVDS. The 642 will give you a simple menu from which you can select the file you want to play. If you can record at a slightly lower bitrate (5800 kbps for a 480x480 file is probably more than you really need) you can fit two files on a DVD.

[TBoneit]

Exactly, why fret about squeezing the most onto a disc. Retain all the quality.

The phillips should play them unchanged. Just do a trial burn and see. That would keep all the quality there is in the files. discs are cheap. Encoding to Divx/Xvid will take time and a decent machine and lower quality.

The files you are seeing form the net most likely will not look all that good on a really decent TV such as a HDTV.

HDTV is in your future and later on you will wish you had kept all the quality there is. If it isn't worth a few extra pennies on discs is it really worth having? Hsaving mad ethe jump to HDTV some f the things I did before and thought they looked OK now look poor and need to be replaced. Unfortunately 1 ytime things can't be redone. Live and Learn!

The ones you are seeing off of the internet are done by people that can take time to process and want to squeeze the last bit of size out of the file so it can be transferred faster. They are most likely lowering the resolution to squeeze 45 minutes into a 350 meg file. Proably other tricks too.

If talking about the files available for rent/sale that are starting to appear they ar emost likely done on professional grade equipment you or I couldn't afford. The MPEG4 realtime encoders that DirecTV and DIshnetworks are using for HD are very expensive and I've heard rumbles that the bandwidth savings are not as large as they'd hoped for in part due to needing to be done realtime.

[mtcabral]

Wow, this is a terrific forum. Thank you all for the great responses and realistic advice.

I'll play around with the suggestions made here, but now agree that my best bet may be just to burn my big files. Not knowing much about the ~350MB files I was downloading before coming here, I thought I might be mssing a shortcut.

I will be back here! Tx again!

Mike