|
|
| endorphin |
 Posted: Apr 4 2003, 06:37 PM |
 |
|
Advanced Member
Group: Members
Posts: 112
Member No.: 3488
Joined: 4-April 03
|
Hello, this is my first post though I've lurked for a while. Like many others I must say that VirtualDub is amazing and versatile and I'm so grateful for its existence; I've been using it for about 2 years now.
I have a bunch of AVIs, some Uncompressed and some DV, that I need to archive to DVD+R or at the very least repack them into HuffYUV for space saving.
I have been running these through VirtualDub using each and every HuffYUV option, and to my dismay the output files are coming out LARGER than the inputs!
Q: "are you accidentally adding an audio track during the dub when there was none before?"
A: No, most of these have no audio and I tell VirtualDub to keep it that way - video only.
Having said that, I'm seeing my output files turn out 2-3X larger than the inputs. What's going on here?
Here are more details of the situation: If I take a clip that was just captured (to a DV AVI) off my camera via 1394 and recompress it via HuffYUV, I do get the expected file size reduction. However, when I have edited and spliced a whole group of clips into a longer video, like a 5 minute video (using Premiere and After Effects, typically) then rendered the video to Uncompressed AVI... I later try to repack that using VDub and Huff and what I get is a file size increase. Furthermore, if I go back to the same Premiere project and render it from there into HuffYUV (to avoid the separate VDub repacking step) the results are the same: larger than Uncompressed.
The only suspicious clue I've got so far is that the video clips in question were shot in 16:9 (not true 16:9 but "consumer level" 16:9 in which my Panasonic digicam stores DV at 720x480 in a widescreen pixel aspect ratio of 1.2, IIRC). So I wonder if it has something to do with processing non-square pixels. But this leads me nowhere because many of the clips which have come out larger via HuffYUV had already been re-rendered to square pixels in the Uncompressed AVI that was the source/input for the HuffYUV repack. In other words Huff was not being asked to deal with nonsquare pixels.
This is the only forum serious enough for me to get a good response on this. I'm willing to experiment, try any actions suggested, and report back.
I'll work with ya... please give me suggestions for figuring this out.
Thanks a lot.
- endorphin |
|
| endorphin |
| Posted: Apr 5 2003, 08:04 AM |
|
|
Advanced Member
Group: Members
Posts: 112
Member No.: 3488
Joined: 4-April 03
|
Also, please let me know if I have posted this in the wrong forum; e.g. if it's more of a Newbie question or for General Discussion. |
|
| fccHandler |
| Posted: Apr 5 2003, 08:37 AM |
|
|
Administrator n00b
Group: Moderators
Posts: 3961
Member No.: 280
Joined: 13-September 02
|
Thanks for the wonderfully detailed post (I wish every question was so well written). Unfortunately, I'm sorry I have no clue what is happening with your encodes.
--------------------
May the FOURCC be with you... |
|
| endorphin |
| Posted: Apr 5 2003, 08:50 AM |
|
|
Advanced Member
Group: Members
Posts: 112
Member No.: 3488
Joined: 4-April 03
|
Allright, it looks like I have been a fool about this. I've discovered that I had not properly taken note of which of my source files were Uncompressed and which were compressed with my Matrox DV codec. After reading through this forum and others I found a copy of Gspot and sorted my source clips into separate groups of DV and Uncompressed. I then found that Uncompressed --> HuffYUV does result in the compression one would expect. It is mostly skiing footage and with a lot of large snowy areas Huff manages to compress it on average 5:1.
So it is only the DV clips that were doubling in size when I attempted to recompress with HuffYUV. So I guess this is nothing more than a basic understanding I should have had long ago: DV files are simply twice as compressed as HuffYUV at its best. Of course that makes sense because Huff is lossless and DV is lossy.
What threw me off was the following logic that I fell into:
1. I know DV is a lossy compression format,
2. But my DV clips were original/unaltered captures,
3. Therefore any form of compression must make them smaller...
4. So which codec to compress with: a fast, lossless one therefore HuffYUV
5. And then I got confused when I saw the file sizes grow larger, not smaller.
#3 was the fault, and it was due to a basic misunderstanding. I now realize that the fact that a clip is an original unedited capture does not mean it's uncompressed.
I must have been capturing in DV all this time when I thought I was capturing Uncompressed (duh!). I have tried to capture to HuffYUV, of course, but have been unable to get it to work. Can't capture in Huff using VDub because of the unsolved WDM<>VFW issues with my plain 1394 card. Should be able to capture to Huff using Premiere 6.5, but Premiere refuses to show a preview on the screen when Huff is selected.
So here are my remaining questions:
* I want to try harder to capture to Huff... what should I try next? Is there ANY way to capture in HuffYUV using VDub with a 1394 card right now, or should I give up?
* Meanwhile, should I worry about capturing in this DV codec that I'm using, since I guess it's a lossy (though not very lossy) format?
* Am I correct to conclude that a HuffYUV encode of a given clip should in fact be larger than a DV encode of the same clip?
* I was formerly under the impression that miniDV footage is stored on tape, at the moment that it is shot in a camera, in a DV codec of some sort -- and I think this is what caused me to incorrectly equate DV with Uncompressed. Stupid of me, of course, because storage in any codec (other than the proverbial 'null codec') means compression is being used.
* What good is the DV codec installed on my machine if it is not the format in which my footage is originally stored on tape, *and* if I also don't want to capture to DV because it's lossy? What use is the DV codec then? Does it only exist as one of many choices that are somewhere in the range of fidelity between HuffYUV and MPEG-2 capture?
I would appreciate any other notes or corrections! Particularly on the subject of how I can successfully capture in Huff.
|
|
| Morsa |
| Posted: Apr 6 2003, 08:01 AM |
|
|
Moderator of the Vdub support board
Group: Moderators
Posts: 640
Member No.: 246
Joined: 9-September 02
|
I will try to answer as many question as I can:
* I want to try harder to capture to Huff... what should I try next? Is there ANY way to capture in HuffYUV using VDub with a 1394 card right now, or should I give up?
-There is no ieee1394 support into Vdub. Use WinDV or AVIio to get you DV.
They are both free.
* Meanwhile, should I worry about capturing in this DV codec that I'm using, since I guess it's a lossy (though not very lossy) format?
Don't worry, because you aren't capturing to DV, in fact you are just copying the EXACT information (more or less) that is recorded into you DV tape. IEEE1394 is just a serial cable that transfers binary data at a maximum rate of 400 Mbit per second. DV needs 25 Mbit per second.
* Am I correct to conclude that a HuffYUV encode of a given clip should in fact be larger than a DV encode of the same clip?
Yes, You are correct. For example if you have a DV AVI file of 100 MB greyscale, when you convert it to Huffyuv in YUV2 compression, you end up with a 150 MB AVI file.
* What good is the DV codec installed on my machine if it is not the format in which my footage is originally stored on tape, *and* if I also don't want to capture to DV because it's lossy? What use is the DV codec then? Does it only exist as one of many choices that are somewhere in the range of fidelity between HuffYUV and MPEG-2 capture?
It Is The Original Format Your Footage Was Originally Stored on Tape. Always Remember That.
DV is far better than Mpeg2 and far worst than huffyuv.DV is like kind of cousin of the famous MJPEG. Digital8, DV, MiniDV, DVCAM and DVCpro all use the same codec: DV. Also DVCPRO50 and DVCPRO100 (AKA JVC's HD) use the same compression scheme but with smaller quantizers (less compression) Even the famous SONY's HDCAM uses the same scheme (7:1 compression ratio)but in a different way AFAIK it uses 5 codec chips in parallel to compress the video stream..
Seen your other post about your video levels problem.The only way is to test another DV codec or to decompress your video, correct the levels and compress it again. |
|
| endorphin |
| Posted: Apr 7 2003, 03:40 AM |
|
|
Advanced Member
Group: Members
Posts: 112
Member No.: 3488
Joined: 4-April 03
|
Thanks again, Morsa -- that was very helpful. Ok, I always thought that DV was the format on tape; I just got confused about that in the last week of asking these questions.
So that brings up another item. Since DV is the format on the miniDV tape, the only way I can capture via 1394 is as a DV file. This would mean that my quest to capture digital tape into HuffYUV has been unnecessary. Capturing with Huff would only be a reasonable thing to do if I were capturing analog material, so I could avoid compressing it. But with footage from a minDV tape, since it's already DV-compressed, capturing to Huff would only be an unnecessary unpacking. Is this all correct thinking?
I guess if I stick with 1394 transfer, I'd still have some use for Huff as an intermediate format. Like when I have applied some processing steps to a video clip but need to save it for a while and work on it later, it woulf be better to HuffYUV-encode it rather than DV-encode it for storage. Correct? |
|
| ChristianHJW |
| Posted: Apr 7 2003, 01:38 PM |
|
|
Advanced Member
Group: Moderators
Posts: 1768
Member No.: 2
Joined: 7-July 02
|
| QUOTE (endorphin @ Apr 7 2003, 05:40 AM) | | I guess if I stick with 1394 transfer, I'd still have some use for Huff as an intermediate format. Like when I have applied some processing steps to a video clip but need to save it for a while and work on it later, it woulf be better to HuffYUV-encode it rather than DV-encode it for storage. Correct? |
You're a quick learner  ....
--------------------
Visit the unofficial Virtualdub support forum on http://forums.virtualdub.org - help to reduce the big number of emails Avery Lee is getting every day !!
Support matroska as container and Gstreamer as the only truely open, x-platform multimedia platform .... |
|
|
