XviD and Interlacing

[Tytanic]

So I've completed capturing majority of my analogue VHS tapes a few months back. Everything went perfectly and I was happy with my results.

However, I remember reading somewhere prior to starting my project that if I am capturing VHS tapes then there would be no need to select the "Interlaced Encoding" option in VirtualDub, so I didn't. Looking at the final product my AVI/XviD files have combing or interlacing in the video, but MediaInfo states the file is "Progressive." So I did some test captures; capturing with the "Interlaced Encoding" setting checked, and even captured in MPEG2 using MainConcept 2.5 with the appropriate settings. Comparing them all they are exactly the same only MediaInfo is labeling the original capture without the setting checked as "Progressive" despite the results all looking the same. Does this mean my captures are truly interlaced but not labeled as such? Should I re-capture everything with that setting checked off? Or should I just leave it as is? I was so happy with my results but this is the only issue bugging me. Note that I've captured about 40 tapes, so if it is absolutely necessary to re-capture then I will.

I've attached an example picture to further illustrate what I am seeing for every capture.

[sanlyn]

Looks like an interlaced frame to me. Can't you tell by playing the video in VirtuaLDub or other editors that don't deinterlace in their preview window?

MediaInfo doesn't always get every detail correct, which also depends on video's internal header info.

There's an interlaced encoding option in VirtualDub during capture? Or did you capture to lossless and encode later? How do you know you're not looking at blended frames? One can encode interlaced video and tell the encoder to encode as progressive. Interlaced video encoded with progressive flags will have what look like interlaced frames but the video will be reported as progressive. Animation is usually created as progressive video with telecine added. Telecined frames look like interlaced frames.

It's difficult to give you an answer from only a single image.

[Tytanic]

I captured directly to Xvid, it would take literally months to encode from HuffyUV.

There was an "interlaced encoding" box in the XviD options when using Virtualdub. If I check that box off MediaInfo identifies the scan type as "Interlaced". But regardless if I check it off or not the pictures are exactly the same each frame which leads me to assume that option only affects the written information that is displayed when using programs such as MediaInfo to view details perhaps (I believe this is called a header?)?

I've attached a raw clip to make it easier to identify.

[sanlyn]

Thanks for the sample and the info.

The avi is from a 23.976 fps progressive original which has pulldown (telecine) applied for 29.97 fps playback. It was encoded as progressive. If viewed in editors that don't deinterlace or remove 3:2 pulldown in their previewers, 2 of 5 frames will appear interlaced. Telecine isn't the same thing as interlacing. It should never be deinterlaced but should use inverse telecine to restore the oiginal progressive frames if you want progresssive video. Deinterlacing would produce chroma ghosting.

Animation is usually created at 15fps with periodic duplicate frames inserted for 23.976 film speed (this one has a 23.976 overlay with the snow, which was overlayed later).

The attached mp4 has been inverse telecined (IVTC) and plays at the original film speed of 23.97fps. I evened up the borders and cleaned the head switching noise at the bottom. This sort of fix and IVTC requires re-encoding, which degrades the image and is one reason why lossless capture is recommended. The original also has some luma flicker and sharpening halos.

[Tytanic]

I see, though if my final destination was DVD wouldn't I need to capture at 29.97fps and interlaced for optimal playback? Assuming DVD is my final destination, what would you recommend?

I just don't have the time or space to capture everything in HuffyUV so I'd just like capture directly to a lossy codec (done right). I've tried capturing to MPEG2 using MainConcept but 2 out of 5 frames appear interlaced as you mentioned. I seriously don't understand why every codec I try wields the same results. I was really happy with my results, but now I''m unsure what to do.

[Tytanic]

Edit: Accidentally double posted same post.

[sanlyn]

Quote:

Originally Posted by Tytanic

I see, though if my final destination was DVD wouldn't I need to capture at 29.97fps and interlaced for optimal playback? Assuming DVD is my final destination, what would you recommend?

DVD is either interlaced or telecined. Again, if you deinterlace telecined video you'll have a damaged capture. For all practical purpose, a VCR plays interlaced or telecined video as interlaced. If you capture interlaced or telecined video and encode it as progressive, many players will play it as progressive and won't treat interlace or telecine properly if it goes by a progressive flag in the video. Encode as interlaced.

Quote:

Originally Posted by Tytanic

I just don't have the time or space to capture everything in HuffyUV so I'd just like capture directly to a lossy codec (done right). I've tried capturing to MPEG2 using MainConcept but 2 out of 5 frames appear interlaced as you mentioned. I seriously don't understand why every codec I try wields the same results. I was really happy with my results, but now I''m unsure what to do.

If you were happy with the results, what changed your mind?

Encode as interlaced or progressive, you'll get the same results. Media players and TV recognize interlace/telecine and play it properly. You watch interlaced and telecined TV shows and movies, and buy interlaced or telecined DVD and BluyRay, don't you? Interlaced NTSC video when properly deinterlaced plays at 59.94fps double frame rate and has twice the number of frames. Is that what you want? You can't use it for DVD. If you do it after you capture you'll have to re-encode and take a quality hit. And most NLE's and capture devices do a terrible job of deinterlacing during capture.

What hardware/software are you capturing to lossy codecs with?

[EDIT] The attached MPG is encoded for DVD. Your original Xvid avi was decoded,then the hard-coded telecine frames were inverse telecined, and the re-encoded with 3:2 pulldown pulldown instead of hard-coded telecined/interlaced frames. On playback I don't see the hard-coded combing effects I see with your Xvid capture.

The mediainfo report on the MPG, below. What kind of header data your encoders are putting in their videos could be different. Mediainfo doesn't scan a video to check out everything.

General
Complete name                            : E:\forum\faq\Tytanic\raw_pulldown_DVD.mpg
Format                                   : MPEG-PS
File size                                : 23.3 MiB
Duration                                 : 34s 208ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 5 705 Kbps
Writing library                          : encoded by TMPGEnc Video Mastering Works 5 Version. 5.5.2.107

Video
ID                                       : 224 (0xE0)
Format                                   : MPEG Video
Format version                           : Version 2
Format profile                           : Main@Main
Format settings, BVOP                    : Yes
Format settings, Matrix                  : Custom
Format settings, GOP                     : M=3, N=13
Duration                                 : 34s 184ms
Bit rate mode                            : Variable
Bit rate                                 : 5 464 Kbps
Maximum bit rate                         : 8 000 Kbps
Width                                    : 720 pixels
Height                                   : 480 pixels
Display aspect ratio                     : 4:3
Frame rate                               : 23.976 fps
Standard                                 : NTSC
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Scan order                               : 2:3 Pulldown
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.659
Time code of first frame                 : 00:00:00:00
Time code source                         : Group of pictures header
GOP, Open/Closed                         : Closed
Stream size                              : 22.3 MiB (96%)
Writing library                          : TMPGEnc Video Mastering Works 5 Version. 5.5.2.107
Color primaries                          : BT.601 NTSC
Transfer characteristics                 : BT.601
Matrix coefficients                      : BT.601

Audio
ID                                       : 189 (0xBD)-128 (0x80)
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Format settings, Endianness              : Big
Muxing mode                              : DVD-Video
Duration                                 : 34s 208ms
Bit rate mode                            : Constant
Bit rate                                 : 128 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Stream size                              : 535 KiB (2%)

[Tytanic]

I captured using VirtualDub and an AverMedia USB device.

I used little compression on the video as you may have noticed to prevent significant or noticeable quality loss in the case I might want to transcode for whatever the reason may be, in fact I can't even tell the difference between your file and my raw capture in terms of picture quality.

But if you still think I would be better off capturing in HuffyUV and encoding to MPEG2 I suppose I can but it would take me ages since I have 40 tapes and over 200 episodes to do.

So your encode is most ideal for burning to DVD? Would you mind sharing details with me for your process of IVTC'ing my file? I'd like to do this for the rest so my final products are error free, and I think your did an excellent job, it looks better/proper when in motion.

[sanlyn]

If you're satisfied with Xvid and don't intend to go through any cleanup such as denosing, there's no real reason to ivtc and re-encode. Xvid isn't a universal format, and not many external players will handle it, but DVD can be played by just about anything and easily copied. If you wanted MPEG2 for DVD you would have to remove telecine from your XVid and re-encode with 3:2 pulldown added. I wouldn't be unduly concerned that some media info app or other isn't reporting its scan type correctly (which happens often enough),
as long as it's playing correctly.

The only application I'd recommend for ivtc would be Avsiynth and its TIVTC plugin, both free. The typical NLE doesn't do nearly as well, and some will simply botch it. The IVTC command is simple enough for 3:2 NTSC pulldown removal: The file is opened and decoded with the first command, then de-telecined with the second. The output would be lossless uncompressed AVI which you can feed to a frame serving editor or to an encoder you have available through VirtualDub. The first line contains a path statement that you would customize to match your system and filename:

AviSource("Drive:\path\to\video.avi")
AssumeTFF().TFM().TDecimate()

Encoding and adding pulldown flags would be a feature of the encoder.

Quote:

Originally Posted by Tytanic

I can't even tell the difference between your file and my raw capture in terms of picture quality.

That's the general idea behind the software and standard methods I used.

[sanlyn]

Oh, I forgot:

Quote:

Originally Posted by Tytanic

II can't even tell the difference between your file and my raw capture in terms of picture quality.

Well,l it's not a "raw" capture. Raw video refers to uncompressed, unprocessed, unformatted image data, not to encoded video. The capture is a formatted lossy encode. Seems a subtle distinction, but you know how some techy readers can get bent outta shape about these things.....

[Tytanic]

Sorry yes that is true, I sometimes unintentionally use it to refer to an original source as opposed to an uncompressed/unprocessed source.

And thank you very much for your help. Now I'm just determining if I should use MPEG2 to encode for a DVD or a more appropriate codec for streaming. But I'm glad I now know how to IVTC my files. I think besides the interlacing issue, I did a good job capturing them. Considering I have hundreds of episodes this should suffice. Honestly I think I'm just going to leave them as is, not quite worth all the time.

[sanlyn]

Yes, if a video plays well (they won't be perfect, ever) it's usually better to leave them as-is. Re-encoding does have penalties if tender loving care isn't used.

Yeah, the terminology is a pain sometimes. I get corrected on a regular basis myself. By the way, I should have added that in the Avisynth code posted earlier, the functions TFM() and TDecimate() are functions from the TIVTC plugin, not different plugins in themselves. And as you can see rom this link to the plugin at http://avisynth.nl/index.php/TIVTC, sometimes things can be too specific.

[msgohan]

In this case, MediaInfo is correct. Your capture is forever damaged: the content is interlaced, but it's encoded in progressive mode. The presence of combing in the capture does not mean that the interlacing structure has been maintained.

One problem here is that the encode needs to use 4:2:0, but you've effectively told the XviD encoder to convert from 4:2:2 using the progressive method instead of the interlaced method. This will cause chroma ghosting on every interlaced frame.

From the original raw.avi:
Tytanic_FoxBox_fi264.png

sanlyn's processed raw_pulldown_DVD.mpg still contains this error.