Coldstreams Online Video

I’ve seen some confusion on the online forums regarding shooting in 30p (or 24p) and then importing into a video editor.

Why does my 30p video show up as 60i in <name your editor>?

In an interleaved 60i video (normal old fashioned video), the image is scanned 60 times per second, producing one half frame at each scan (say the odd scan lines, followed by the even scan lines in the next half frame). Because movement can occur between the two half frames, you some times see interlaced jagged edges.

A better way is to take 30 still pictures per second of the entire image.

When your camera records at 30p video, it takes a single image – but splits it into two half frames and stuffs those into two 60i half frames (without any jaggies since its splitting one image in to two pieces whereas 60i creates one image from two separate pieces taken 1/60th of a second apart).

Consequently, a 30p video is stored as a 60i video. And two consecutive half frames, put together, become 30p. Your video software can’t tell the difference between between 60i and 30p.

So why do we have these strange 60i half frames? Historic reasons. The earliest TVs were not able to scan the full image top to bottom before the next image would arrive. The solution then was to draw only half the lines in each interval. Thanks to the persistence of the phosphor image of old TVs, the first lines remained glowing while the TV then scanned the alternate lines.

No one would design a TV like that today – but we’ve lived with it for many decades and it is still supported for compatibility reasons.

I can import 24p video into iMovie (or other editor) but it plays weird – why?

This depends on the camera. But it is common to store the 24p image in half frames, similar to 30p. But since 24 does not evenly divide into 60, the sequence of half frames is a little different.

In 30p, the sequence is basically 2:2:2:2:2:2 and so on where the 2 signifies 2 half frames.

In 24p, the video may be stored in various combinations such as:

2:3:3:2 or 2:3:2:3

In this way, the 24p mode uses up more half frames – consider 2 half frames and then 3 half frames. This slows down the video frames to match the 60i storage of the tape. Consequently, 24p gets mapped into a funky sequence of half frames on the 60i tape.

To a program like iMovie, this 24p footage looks just like 60i. But unfortunately, iMovie (And many other video editors) have no way of knowing that it is not really 60i footage with some frames appearing 3 times. So play back and edits produce strange artifacts.

If you want to convert this to proper 24p footage and then edit in an editor that supports 24 frames per second see these instructions.

HD videos uploaded in 1920 x 1080/p will – probably – be transcoded by Youtube into 1080p videos. This represents an upgrade from Youtube’s 1280 x 720p maximum HD resolution.  (“Probably” because Youtube says not all videos will be converted just yet.)

The 1080p videos, however, are useless for most computer displays as few have 1920 x 1080 sized displays. The main advantage, probably, is that in a near future world, we will be watching streaming videos over the Internet – on our real HDTVs, arriving via a set top box.

Worse, you’ll need a very fast processor to watch the new 1080/p HD videos. I can’t watch them on a 3.2 Ghz Windows OS computer – and I can watch them on my quad core Mac Pro only if I wait for the video to download entirely, first. The problem is the video stutters badly as the processor cannot keep up with the Flash video decoding.

Recommendation: Upload the HD video but don’t select the HD option during play back.  It looks like the new “normal” is 1280 x 720 – so you don’t need to select HD.

uploading Failed upload aborted – YouTube Help.

Just an FYI – this is happening to me, also. It has been impossible to upload videos to YouTube the past couple of days. Actually, I can upload short videos, say 30 seconds long – YouTube gives an error but processes the video anyway. Longer videos, such as 5 minutes, always fail. I suspect this is due to YouTube’s new 1080p upgrade not working.

Nothing changed on my end – or for the many others experiencing this problem. Today is Saturday, November 21, 2009 for reference.

There is a work around, apparently: Use the multi-video or bulk video upload option. This does work for me and others.

As you may know, YouTube now supports both HQ (high quality) and HD (high definition) videos.

To create an HQ video, you need to upload a video file encoded at a rate of at least 1.5 Mbps.

To create an HD video, you need to upload an HD video file encoded at a rate of at least 2.0 Mbps.

YouTube recommends transcoding your HD video to 1280×720 prior to upload. This does work and produces a good quality HD conversion.

But here’s a little secret that I verified with some tests – don’t use 1280×720. Instead, transcode your video to 1920 x 1080. This produces the best YouTube HD video quality if you encode with sufficient bits.

Here is a video I shot in HDV (1440 x 1080/24p) – and after editing, transcoded to 1920 x 1080 / 24p H.264 at 5 mbps. The resulting huge file was then uploaded to YouTube. Watch it in “HD” and “Fullscreen”. Looks pretty sharp, heh?

(Sorry about the long zoom camera shake at the beginning – I was also dealing with someone else’s medical emergency as I tried to keep my mind focused on shooting this.)

Another trick for online use, if your camera supports it, is to shoot at 24p – that is 24 frames per second, progressive mode. There are three advantages to do this:

1. You avoid the interlace jaggies by shooting in progressive mode
2. You have fewer frames/second to process on your computer when re-encoding in to h.264 for upload, so this step is 20% faster
3. There appears to be a slight improvement in image quality.  While h.264 does interframe compression across a group of frames, there is a slight advantage in having fewer frames for a given data rate – so your encoding quality is a little bit better.

Shedworx has upgraded their VoltaicHD AVCHD and 24p inverse telecine software to version 2.0

The 2.0 version now appears to successfully convert my Canon HG10 AVCHD/24p footage into the proper format for editing. Yay!

It’s not real fast and the converted files are big but it does work now …

There is an option, supposedly, in Preferences to change the Quicktime output format to another codec. To make that work, you must also select the Convert (Custom) option.  However, so far, I have not achieved the results I was trying to get – I will keep working on that and hopefully post something back later.

The free alternative is to import the AVCHD into iMovie 9, and let iMovie convert to large AIC files (up to 4 to 5 times bigger!). Then, run those through the free JES Deinterlacer set to inverse telecine to 24p.  While this free method is time consuming, it mostly runs on autopilot – so I import the files to iMovie and walk away. When done, I then set up JES Deinterlacer to do the conversion to the new file format (creating more AIC files…).

Once completed, I delete all the files I don’t need and then go edit in Final Cut Pro. There, set your timeline sequence to AIC encoding and you will not have to do any rendering to see your AIC imported media clips.

VoltaicHD also provides several other features now – including deinterlacing of interlaced video, direct conversion to 1280×720 and upload to YouTube automatically. (You can also have it automatically convert to Apple TV or iPhone formats.) If you happen to have a 35mm lens adapter – used for creating deep depth of field on video cameras – your images end up flipped around. VoltaicHD has a new option to re-orient your video back to the proper orientation.

I have not yet tested the de-interlacing support but this could be useful for odd cameras like the HG10 which omit a 30p video capability. Shoot in 60i and let VoltaicHD transcode your AVCHD and deinterlace to 30p all at the same time. I’ll have to give that a whirl!