Quality questions:Conversion from AVi to MP4

[kittykaboodle]

Hi,
I have a number of avi's and was wondering if I convert it to MPEG4 format, what will the loss of quality be?
Will I loose less quality if I convert it to MPEG2.
What should I do.

I looked at the chart comparision, in Videohelp, and it seemed to tell me as if MPEG4 was lower quality than MPEG2. Perhaps I didn't understand that chart.

Please advise.

Kitty Girl
http://www.msdivine.net

[jagabo]

Any time you convert using a lossy codec (like MPEG2 or MPEG4) you will get some loss of quality. If you use a high bitrate the loss may not be noticable.

MPEG4 isn't necessarily lower quality than MPEG2. It's just that MPEG4 is more often used to squeeze files down to very small sizes for easier internet transfer. If you encode a particular high quality source with both MPEG2 and MPEG4 at the same bitrate the mPEG4 will look better.

Note that AVI is a container. It can contain video and audio with just about any type of compression, even MPEG2. What exactly is your source (DV AVI from a camcorder?) and objective (DVD, internet distribution)?

[kittykaboodle]

Hi there,
Thanks for the quick response.

The avi files that I am using, are files that I obtained after transferring it from my digital camera to the harddrive via Adobe Premiere. I have edited my movie and it is just giant 6 gig avi file.

There are several things I was hoping to do:

1) I eventually wanted to collect all my movies in avi file and burn it to a DVD of high quality. However, I have a ton of movies and am not sure when I will do it. So I was wondering if by storing it as MPEG4 , the quality will be good. Then when I am ready I can convert it to DVD without any loss of DVD type quality.

But I read that DVD uses MPEG2 format. WOuld it be better if I converted my avi to MPEG2 format?

2) I have a weekly cable access show. The 30 minute show takes up about 7 gigs.
I was wondering, if I can convert it to MPEG4 for archival puporses.
Then if I do need to do a re-run of my show, can I convert my
MPEG4->AVI then export it to MINI DV. Will there be any noticeable loss of quality on a television screen?

3) Is it true to assume that AVI (DV) will always have the best quality, while mpeg2 and mpeg4 will have a bit of a loss of quality.

Please advise.

Ms. Divine

[jagabo]

The avi files that I am using, are files that I obtained after transferring it from my digital camera to the harddrive via Adobe Premiere. I have edited my movie and it is just giant 6 gig avi file.

OK, you are starting with DV AVI.

There are several things I was hoping to do:

1) I eventually wanted to collect all my movies in avi file and burn it to a DVD of high quality. However, I have a ton of movies and am not sure when I will do it. So I was wondering if by storing it as MPEG4 , the quality will be good. Then when I am ready I can convert it to DVD without any loss of DVD type quality.

But I read that DVD uses MPEG2 format. WOuld it be better if I converted my avi to MPEG2 format?

If you want a DVD that will play on normal DVD players you have to use MPEG2. There are some players that will play MPEG4 (Divx/Xvid) encoded AVI files but they are a minority.

A further problem you will have is that most of the video you'll be working with is interlaced. Some of the MPEG4 encoders support interlaced encoding but I don't know of any players that handle it properly, either on a computer or set-top Divx/DVD player. So you'll have to inverse telecine or deinterlace to get an acceptable MPEG4 video for playback on TV with at Divx/DVD player.

Other than that, you can store video as MPEG4 at about half the size of MPEG2 with the same quality.

2) I have a weekly cable access show. The 30 minute show takes up about 7 gigs.
I was wondering, if I can convert it to MPEG4 for archival puporses.
Then if I do need to do a re-run of my show, can I convert my
MPEG4->AVI then export it to MINI DV. Will there be any noticeable loss of quality on a television screen?

If you use high bitrates for the conversions there won't be much degradation of the picture. Can the studio accept your video on regular movie (MPEG2) DVD? I think that is a better compromise. Even the noisiest, shakey, hand-held camcorder footage will look decent encoded at one hour per DVD. Clean footage from a tripod mounted camera will look good up to about 2 hours. For VHS sources you can drop the resolution down to 352x480, use a lower bitrate, and get even more running time on a DVD (without much loss of quality).

3) Is it true to assume that AVI (DV) will always have the best quality, while mpeg2 and mpeg4 will have a bit of a loss of quality.

Generally yes. But again the loss may not be very visible after a single generation of transcoding.

[redwudz]

Your 6GB file I would either split to 2 DVDs or one dual layer DVD. Don't compress it any further if you want to preserve the highest quality.

If you want something to play on a regular DVD standalone player, you need to use MPEG-2. As long as you have the original 6GB DV file archived, go ahead and convert it to MPEG-2. I would use a decent encoder, TMPGEnc or similar. That way you should preserve most of the quality. And you would have a DVD that will play on most any DVD player.

If you want to archive your videos, two choices. Leave them on a DV tape. It will survive quite a long time. Or burn the DV to DVD as a data disc. It might take a few discs, but they are cheap enough. You will have no quality loss either way.

As far as day to day storage of video from captures from TV, etc., MPEG4 is a great alternative to MPEG. It's very compact. Decent quality. But not for something I want to preserve for the next generation.

If you want to convert a MPEG4 back to a MPEG-2, you will have losses. Think of it as SVCD quality or VCD quality, worst case. It's fine on a small TV but not so good on a large one. Still, the rule should be, use as much storage room as possible, DVD is a minimum. If you have to split it to two DVDs, do it. It may take a little longer, but you won't regret it in the future. Buy a bulk pack of about 200 DVD blanks and don't be stingy. Just my opinion.

[kittykaboodle]

Hi there,
Thanks for all your help.
I still have more questions.

Yes, I do back up my completed avi movie to DVD as a data avi file, and then i back it up to mini dv tape.

However, I will want to make a playable DVD in the future, but at the moment don't have time for the menu layout.
What do I do with my avi files while I wait.

Here are more questions I still have for I am a bit unclear still.

1) I thought if I use high bitrates, converting from MP4 to Mpeg 2 wouldn't make have loss of quality . Is this true?

2) So archiving it to MPeg 4 and then converting it Mpeg 2 , to play in a DVD is then not recommended due to loss of quality? Is this true?

3) Also if I were to archive my avi files to mpeg 2 (so that in the future I can burn to DVD as a DVD movie), what is a good setting to use. What are good bitrates to use.
I am using the big Nero suite.

well thanks again for your quick responses.
And yes, I have gotten over my stinginess with blank DVDs.

[celtic_druid]

As said MPEG-2 is lossy, so there is always a quality loss, although yes, given a high enough bitrate you probably won't notice.

mp4 allows for AVC, which is capable of lossless encoding, so it isn't true that mp4 is always lossy. On the audio side you have ALS which is also lossless. Problem is that DV isn't lossless so your size is going to go up. Also I think that the only current ALS encoder is the reference one.

[guns1inger]

Given the run time is somewhere between 25 and 30 minutes, you can encode this at CBR 9000 and I doubt you will notice any difference between the DVD version and the original.

[kittykaboodle]

Hi there,

1) When I am using Nero, I do not see the option to use CBR 9000. How do I set this option. Is this going to be an Mpeg2?


2) So I am still a bit unclear. Is it better to encode it at MPEG2 for future use to convert to DVD. Or should I encode it to MPEG4 so that later I can convert it to DVD. MPEG4 vs. MPEG2. which is recommended with regard to quality.

3) In the Nero Dialog box when making it into an MPEG 2. It has several options.
WHat would one recommend for instance:

Sample Format:
Progressive
Interlaced (TOp field first)
Interlaced (bottom field first)
Automatic

Encoding Mode: Fast Encoding (1pass) OR High Quality (2Pass)

What is the recommended BIT RATE?

What is the recommended Audio Format. The options are:
Automatic
Dolby Digital (AC-3)5.1
Dolby Digital (AC-3)2.0
LPCM

4) I have a DVD clip on DVD. I need to convert it to AVI to import via my digital camera. Using Nero, after ripping the DVD. Should I convert the vob files to MPEG2, then convert to AVI>
Before, I would convert these files to MP4(thinking its high quality) and then to AVI.
Which conversion would result in better quality.

Thanks for your help. I apologize if my questions seem silly, but I am just a bit confused right now, and that's why my questions may seem repetitive.

[whitejremiah]

you need to use an mpeg encoder...........check the conversion section of the forums for various programs and such...if your not looking to spend any money, though, SUPER is a good place to start, and it generally produces some pretty good results..........like what was said, given your input source, i doubt there would be any SIGNIFICANT quality loss if you encoded straight to dvd with a bitrate of even 6000-7000k/s would work good enough....once you hit 9000k/s though, you can actually start breaking compatability with some dvd players........

[jagabo]

Wrote most if this earlier and came back to finish. I see the discussion has moved on but I'll post it anyway...

1) I thought if I use high bitrates, converting from MP4 to Mpeg 2 wouldn't make have loss of quality . Is this true?

Every time you convert using a lossy codec there will be some loss of... let's say "information". Whether the loss is visible or not depends on how well you perform the conversion (the tools and the codec settings) and how closely you look at the results.

2) So archiving it to MPeg 4 and then converting it Mpeg 2 , to play in a DVD is then not recommended due to loss of quality? Is this true?

You'll have to decide for yourself if the loss is important to you. Keep in mind, if you start with a DV AVI file, convert to MPEG4 and then convert to MPEG2 you are performing two lossy conversions. So you will have more loss than if you went straight from DV to MPEG2. And of course, you're spending ~twice as much time converting.

3) Also if I were to archive my avi files to mpeg 2 (so that in the future I can burn to DVD as a DVD movie), what is a good setting to use. What are good bitrates to use.
I am using the big Nero suite.

Note that you can archive your MPEG2 files in exactly the same way as your MPEG4 files -- just as data files on ISO data disks. You don't have to create movie DVDs with pretty menus and such. Many DVD players will even play MPEG files on ISO data disks. If you don't care about movie DVD compatability you can even use bitrates higher than the DVD spec allows for. But there comes a point where the MPEG files will as big as the DV files so there's no point.

For archival purposes and DVD compatibility you should use 720x480 (same frame size as your DV AVI) and 8000 to 9000 kbps MPEG2 encoding.

Regarding NVE, elect to make a DVD, press the More... button to bring up more options, press Video Options to bring up the Video Options dialog, and press the DVD-Video tab:



I don't use NVE much but i'm pretty sure those are the settings you'll want. Close the options dialog to go back to the main window, the select Export to save as an MPEG file.

[kittykaboodle]

Hi there,
It's been a while since, I visited this forum. Thanks again for all of your help.
I have a 2 questions regarding the last post.

1) With regard to the NVE setting, what is the difference between using Fast Encoding (1pass) or the other option which is (2pass). it says the 2 pass is higher quality. Is this recommended?

2) Also another person recommended that I burn to ISO disks. I also have a question about that.
What if I burn say, a 30 minute avi file to the Video_TS folder as a VOB file using Nero without any menus etc.
Then when I am ready to make a DVD-VIdeo I add the video _TS folder and add menus then burn to dvd disc. Is that a loss of quality, because I burnt it to video_TS (VOB) files and then make the dvd later?

Thanks,
http://www.msdivine.net My little short comey sketch films[/url]

[redwudz]

2 pass encoding uses the first pass to make a 'map' of the video to make the most efficient use of the bitrate available. Fast motion in the video needs higher bitrate, static motion video needs less bitrate for a given quality result. This really pertains to variable bit rate encoding. The second pass is the actual encoding. This usually results in a better encoding, but it will take a lot longer. It's a good choice if you want to use a lower bitrate. If you are using a high bitrate, constant bitrate, not so useful.

You wouldn't want to just make a VOB file and put it in a VIDEO_TS folder. You would need the rest of the DVD files for it to be DVD compliant. Just burn it as a MPEG file in data mode if you don't want to author it. Authoring doesn't really change the MPEG file, just adds the rest of the DVD structure and menus, etc., usually about 200MB.

See 'What is' DVD to the upper left for the DVD structure. <<<<<<

[kittykaboodle]

Hi there,
THanks for your prompt reply.

When I meant that I burnt VOB files for storage in the video_TS files, I meant that there are some other smaller files that created as well in addition to the vob files. I was wondering if that's ok for storage to burn at a later date.

With regard to the burning as MPEG and then coming back later to do the DVD-Video. What sort of settings would be for a good MPEG quality format?
I noticed that in Nero burning to MPEG 2 options are the same as burning to DVD-VIdeo.
So I am wondering if i burn the AVI file to MPEG 2 then burn it to DVD-Video at a later date, will there be a loss of quality with regard to the fact that I burnt it to MPEG 2.
Also if i burnt it into the videoTS folder, will there be a loss of quality with regard to dvdvideo.

Is it normally recommended to burn AVI files to MPEG 2 on hard drive if i want to make dvd video later? What do you recommend.

Also what's a good audio setting?

WIth regard to 2 pass coding. I have no problem if it takes a long time to burn, but I'd like to know what is recommended. I mean because the description in NEro says "High Quality" 2 pass, I feel that is better. What do you think.

Pardon me, if the questions are too repetitive but I am just in the begining stages.

Thanks again for your help.

[jagabo]

1) With regard to the NVE setting, what is the difference between using Fast Encoding (1pass) or the other option which is (2pass). it says the 2 pass is higher quality. Is this recommended?

2-pass (variable bitrate) encoding is higher quality if you use low bitrates. At high bitrates CBR and VBR give about the same quality. If you use ~9000 kbps as I recommended earlier you might as well save time and use 1-pass CBR. Of course, you'll only get about 1 hour of video on a 4.7 GB DVD.

2) Also another person recommended that I burn to ISO disks. I also have a question about that.
What if I burn say, a 30 minute avi file to the Video_TS folder as a VOB file using Nero without any menus etc.
Then when I am ready to make a DVD-VIdeo I add the video _TS folder and add menus then burn to dvd disc. Is that a loss of quality, because I burnt it to video_TS (VOB) files and then make the dvd later?

VOB is basically a repackaging of MPG. You can easily convert back and forth between VOB and MPG without losing quality. Many DVD mastering programs want MPG files as a source so I recommend exporting from NVE as MPG files rather than VOB. When you're ready to master (make pretty menus and stuff) the MPG files will be repackaged as VOB for DVD.

If you're talking about adding more stuff to your VIDEO_TS folder using the same disk later on (so as not to waste space on the DVD), I don't recommend it. That will require multisession burns which is likely to cause problems when you try to playback on a DVD player.

Your best bet is to convert your DV AVI files to MPG, save your MPG files on ISO data DVDs (you can use multisession for this), then when you're ready to master a movie DVD copy the MPG files from your data DVDs to your hard drive and work from there.

[kittykaboodle]

Hi there,
Thanks for your help. I shall definitely use your tips. Thanks so much.

I have one question with regard to the audio setting in Nero. You mentioned earlier to use (Dol

Would it be bad if I used 9000 kbps setting but did 2 pass setting? I mean would I just be redundant or will the file be really big?

Thanks again..

[kittykaboodle]

Oh and 1 more thing wouldn't 9000 kbps rates have a bit of a compatible problem with some dvd-players?

[redwudz]

9000kbps 2 pass would be overkill, probably no increase in quality, but a BIG increase in time to encode.

9000kbps is within specs for all but a few players, but drop it down to 8500 if you're worried. 9800kbps is max video bitrate from 'What is' DVD to the upper left. <<<<<<

[jagabo]

2-pass encodes allow the codec to use more bitrate where it's needed, less where it isn't, and still meet the requested average bitrate. For every scene where the codec uses more than the average it has to find a scene somewhere else to make up for it.

The DVD spec is about 10,000 kbps for video and audio combined. Since you'll probably have stereo audio from your camcorder 256 kbps AC3 is sufficient. 9000+256 probably leaves enough headroom for players that have trouble reading DVDR media. If you want to be really safe (or if you're going to use uncompressed LPCM audio) try 8000 instead.

If you are working near the top end of the valid bitrate for DVD, say 9000 kbps, then there will be little difference in quality between an "action" segment of 9000 CBR and the same segment with VBR that gets encoded at 9600 kbps (typically the max because people usually reserve room for 384 kbps 5.1 channel AC3 audio). Even if you looked at enlarged still frames you'd hardly be able to see a difference -- and even then you probably couldn't really say which is better.

Why don't you try both and see if you can detect a difference. Every video is different.

One thing you should be aware of: handheld camcorder footage is usually pretty shakey and all but the best camcorders produce a fairly noisy picture. All that shaking, zooming, rotating, and noise make it difficult to compress -- it all looks like high action to the codec. So a 2-pass VBR encode will have problems finding "quiet" parts to encode at lower bitrates.

[kittykaboodle]

Hi there,
Thanks for your help.
i appreciate all your tips. The constant 1 pass makes more sense, since I am using a high bitrate.

It seems that my other question got cut off in my earlier post. I was wondering about audio quality that you reacommended. You see in your suggestion you said to use Dolby 2.0, but the other option in the drop down is 5.1 dolby. Wouldnt the higher number be better. What would be the difference?

[redwudz]

Stereo VS 5 channel surround sound. But if you only have stereo (2 channel) in the first place, 2.0 is all you really need. I'm assuming you are still converting from DV video to a DVD? If you do have a 5.1 source, such as a commercial DVD, then you should use 5.1.

[kittykaboodle]

hi there,
Yes, I am still converting movie files that are transferred from mini-dv to be burnt unto dvd-video.
Does this mean then that the sound wasn't 5.1 dolby sound. The thing is, I don't know the difference btwn, 5.1 and 2.0. What is it?

[jagabo]

5.1 has 5 audio and one subwoofer channel (most modern movie DVDs have this), 2.0 has only two audio channels. All you have is 2 (stereo) from a DV camcorder.

[kittykaboodle]

Hi there,
Thanks for your help.
I still have a few more questions and am wondering if I should have posted it under another topic.

1) If I convert my avi file to mpeg 2 file using 9000 constant bitrate, will there be a loss of quality if I come later on, to add this mpeg file to make a dvd-video and then make the dvd-video produce at 7000 constant bit rate.

2) If I convert my avi file to mpeg 2 file using 7000 bit CBR rate, then I come later to add it to make a dvd-video , using a 7000 constant bit rate . Will there be a loss of quality. Will there be further compression done on the already compressed video.

I guess the bottom line is that I read in some books that said when making dvd-video always use the best quality video file that you have.
So I am wondering if its best to use the avi->dvd-video for better quality?
But I would like to make my mpegs because it takes up less space and store it and make dvd's later. but if there is a loss of quality, i'd rather not.
Please advise...

[edDV]

1) yes, some. Every time you convert formats or resample, there is some loss.

2) no. If you know now that you will be using 7000 Kb/s and don't intend to filter further, then use 7000 now. It can be cut without loss later with the right tools.

For best quality or if you want future flexibility keep it in DV format until you know exactly what you want to do, and then encode once for DVD.

[kittykaboodle]

In response to your answer of #2, I am using Nero Express to make the dvd-video. But what are the right tools? is nero ok?

Are you saying then the safest thing it to keep it in dv format before encoding it, because thats the best way of retaining optimum quality.

Also does merging 2 avis into one using nero express dvd-video and choosing the "merge titles" have anything to do with loss of quality. I mean just wondering if some sort of compression or something was done for that.

[edDV]

In response to your answer of #2, I am using Nero Express to make the dvd-video. But what are the right tools? is nero ok?

I'm fairly certain Nero Express will reprocess MPeg2 anytime you use it. Each reprocess will decrease quality. If you encode to 7000 Kb/s, a program like Womble MPEG2VCR can fine edit a MPeg2 file without a full reprocess. Others like TMPGEnc DVD Author can cut on I frames (within a few frames to a second or so of where you want the edit).

Are you saying then the safest thing it to keep it in dv format before encoding it, because thats the best way of retaining optimum quality.

Yes, and DV format makes the best archive for the future if the video is high quality.

Also does merging 2 avis into one using nero express dvd-video and choosing the "merge titles" have anything to do with loss of quality. I mean just wondering if some sort of compression or something was done for that.

If you merge two DV-AVI files into a single DV-AVI file, or record the trimmed segments back to DV tape, you shouldn't see any loss. This assumes Nero Express behaves like similar programs of it's class.

I routinely trim DV camcorder material and record the resulting clips back to tape for later use.

Are these files from a DV camcorder or a digital still camera?

[kittykaboodle]

hi there,
Yes the files are basicall files from a dv camcorder, that I edited in premiere 6.1 and created an avi file with.

I am still a bit unclear about something. You mean even if I encode my avi to mpeg 2 using 7000 cbr, then when i feel ready to make the dvd-vide with the menus and stuff, adding that 7000 cbr mpeg 2 file is going to be "recompressed again' even though I plan on making the dvd-video at 7000 cbr rate. Nero express does this??
I guess nero express isn't that great a software then..

[edDV]

hi there,
Yes the files are basicall files from a dv camcorder, that I edited in premiere 6.1 and created an avi file with.

I am still a bit unclear about something. You mean even if I encode my avi to mpeg 2 using 7000 cbr, then when i feel ready to make the dvd-vide with the menus and stuff, adding that 7000 cbr mpeg 2 file is going to be "recompressed again' even though I plan on making the dvd-video at 7000 cbr rate. Nero express does this??
I guess nero express isn't that great a software then..

Not if you just include the existing clip on a DVD. If you edit it, then it will recompress.

[kittykaboodle]

hi there,
I just plan to add the mpeg 7000 cbr file to Nero express and then make menus and stuff, and then burn the dvd-video under 7000 cbr. So then it doesn't recompress?

but if i were to add the mpeg as 9000 cbr to nero and burn dvdvideo under 7000 there will be loss of compress because it will be recompressing again?