Category Archives: Editing

Editing, Techniques

Why does my 30p video show up as 60i?

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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.

Editing, Techniques

The Mac, AVCHD and 24p

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The only workable solution I have found for editing 24p video from my Canon HG10 (AVCHD) on Mac OS X is to:

1. Use iMovie 9 to import and transcode the AVCHD video to Quicktime AIC video files. Keep in mind that 24p on the Canon and some other cameras is actually stuffed into the 60i interlaced video stream. So you can import into iMovie even though iMovie does not know what to do with the 24p frames. (Note  – I only have Final Cut Pro 5 which does not support AVCHD. The newer versions, 6 and 7, do support AVCHD directly, although as best I can tell, they do not support the 24p stuffed into 60i video streams directly. So you still have to do the next step.)

2. Use the free JES Deinterlacer’s inverse telecine feature to remove the 2:3:3:2 pulldown from the previously converted AIC file. Just look in your Movies Events folder and let JES Deinterlacer process the imported movie clips. Let JES transcode the input back out to AIC files.

3. At this point, you now have 24p AIC files. You’ll need to run Final Cut Pro to do a good job of editing 24p because Final Cut Express doesn’t do 24 fps timelines. In FCP, set your timeline compression sequene to use the AIC compressor – that way you don’t have to render the AIC files to some other format. Drag your inverse telecined 24p files into Final Cut and have fun editing.

Timewise, this process is actually pretty fast. AIC files do “explode” to about 3 to 5 times larger though, than their original AVCHD format. The newer versions of Final Cut support ProRes422, which is a more compact compressor with excellent quality. But if you don’t yet have FCP 6 or 7, that option is not available.

So why go through this trouble to edit 24p? For me, I like progressive images much more than interlaced. However, 24p enables shooting at 1/24th or 1/48th shutter speeds, making it ideal for low light situations.

Update: VoltaicHD’s problems, noted in the next paragraph, have since been fixed. More here – VoltaicHD now works fine on the HG-10 and presumably more cameras too.

Update: Cineform Neo Scene, for both Windows and Mac, appears to do AVCHD conversion and 24p pulldown removal for 24p embedded in 60i streams. Costs $129.

Other options? I’ve tried VoltaicHD, whcih is recommended by many for transcoding AVCHD files to AIC on the Mac (both Intel and PPC versions). VoltaicHD includes a 24p feature that is supposed to remove the pulldown. But based on my testing with the Canon HG10, it only works some of the time. Some clips are successully processed while others have no pulldown removal. I’ve done many experiments with the settings and have concluded that VoltaicHD probably only works on pulldown removal on the 3 specific cameras they list on their website, even though the underlying data formats should be identical. Thus, don’t buy VoltaicHD for the 24p feature unless your camera is specifically listed.

Editing

How to mix HDV and AVCHD on the Same Final Cut Time line

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Originally I planned to use Roxio’s Toast 10 to import AVCHD footage into HDV format video and then edit that, together with other actual HDV video, using Final Cut Pro version 5 (which does not support AVCHD).

However, the Toast 10 feature to import AVCHD and convert to other formats does not work – in fact, per Roxio support, the AVCHD import feature is broken and produces video that is not synchronized with the audio.

I have, however, found a work around that works well for me – and does not use Toast.

I am using iMovie to import the original AVCHD – this automatically transcodes to QuickTime movie files containing Apple Intermediate Code (AIC) encoding.

Then, run Final Cut Express HD (version 3.5.1). FCE HD supports HDV, it turns out, by converting HDV to AIC – so the clips are stored in AIC format. (Final Cut Pro, on the other hand, works with HDV encoding directly and so imports HDV as HDV.)

Next, import the video clips created by iMovie (in the Movies, Events folders – or other location if you chose a different location during import) into Final Cut Express HD. Once in your bin of clips, you can drag these clips directly to the FCE time line. Since the time line is set for AIC encoding, there is no need to render from one format to the other.

I am fortunate that I kept the older Final Cut Express HD on my computer after upgrading to Final Cut Pro. Combined with the new version of iMovie – which automatically handles AVCHD conversion to AIC – this works very slick.

I’m going to see about returning Toast 10 and getting a refund. Toast 10 is very buggy and some of the features claimed for the product on the Roxio web site do not actually work.

Separately, it is probably possible to import HDV and transcode to AIC in Final Cut Pro version 5. I haven’t tried that yet but I think of the option settings likely required to make that work. Then FCP could be used to do the same editing, all in AIC. (You can set the timeline codec to AIC so that you do not have to constantly render the video.)

Editing, Techniques

Working with AVCHD on the Mac

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I do nearly all of my video editing now on a Mac so this post is about processing AVCHD files on the Mac.

Easiest Import

The easiest way to deal with AVCHD is to let iMovie (latest version) import and transcode to the Apple Intermediate Codec (AIC). If you want, you can then edit in iMovie. If you wish to edit in older versions of Final Cut Express or Final Cut Pro, you can import the Quicktime .mov files created by iMovie. Set your timeline sequence encoding to the Apple Intermediate Codec. You can now edit copy your clips direct to the time line, edit as much as you want.

Converting AVCHD to HDV Format

If you must edit both original AVCHD video and HDV video into a single time line and do not want to spend lots of time rendering video clips from AIC into your HDV timeline, then it may be useful to convert AVCHD direct to HDV. If you do not need to merge with HDV footage, then you will not want to do this at all!

Toast 10 from Roxio is the only product that has successfully done the transcoding from AVCHD to HDV (for me). Toast can import your AVCHD files directly from the camera and then re-encode into HDV file format. You do lose some quality (but not very much that most people would actually notice) by re-encoding into HDV.

UPDATE 2009: The Toast 10 product has been riddled with bugs (defects). The company  came out with a 10.0.2 fix release five months later but much is still broken. Worse, the AVCHD conversion feature in Toast 10 DOES NOT WORK. Their decoder gets the video and audio out of synchronization. It does not matter whether you convert from AVCHD to AIC or to HDV. The synchronization will be off. Roxio knows about the problem but after many months has not yet produced a fix. I recommend that you do not purchase Roxio Toast 10 at this time. (Its now 2012 as I revise this text – presumably this has been fixed but I have not gone back to check.)

24p

If you have a consumer camera with 24p capability, you probably cannot directly edit the 24p video without first doing a conversion. But before you consider shooting in 24p, ask yourself if you’d be better off shooting 30p progressive? If you have sort of last year’s Canon camera (HV20, HG10, HG20), you can, in fact, shoot 30p progressive using a simple trick:  Use the Program mode and the Tv selection to set your shutter speed. Set the shutter to 1/30th of second. Your camera now records in 30p mode! This is because the camera actually contains a progressive imaging system-with a 1/30th second shutter speed, both “fields” of the 60i video are recorded without any field shifts. You get perfect 30p, as long as the 1/30th of a second shutter speed is acceptable. (Most 24p is shot at 1/48th or 1/24th of a second. Many people like the blurred motion effect of the slow shutter speeds. Your choice). This trick actually works on a wide variety of older cameras too. If you have a newer camera with true 30p, you may wish to use 30p for all your shooting since it can be directly processed for online or Apple TV/XBox360/PS3 viewing without having to de-interlace.

If you do use the 30p trick, just import your video as 60i and edit as usual. That’s all there is too it.

But if you choose to use 24p, then you must do a “reverse telecine” (or sometimes called “de-telecine” or “inverse telecine”) step to convert the recorded 24p to a true 24p that can be edited in Final Cut Pro. (Final Cut Express and iMovie do not edit 24p video).

VoltaicHD ($35) claims to do the conversion but the demo version did not do so successfully for me. However, if it works, you can use VoltaicHD to import and do telecine removal in one step, producing the AIC files for editing. If it worked, this would be my preferred solution.

HandBrake (see next section) also claims to do reverse telecine conversion but it failed to do so properly on my HG10 video stream. However, its output format is MP4 which is not ideal for video editing.

JES De-Interlacer does do reverse telecine and does it properly and very well (and also does excellent de-interlacing as well as several other features). And its FREE! To use, first import the 24p AVCHD files in iMovie. Then, find the converted files (.mov) in your Movies Events folder. Run JES-Deinterlacer, select all of your input files, and the options page, select the “inverse telecine” option. On the output page, specify a folder to store the converted files – and set your output file format to AIC (Photo JPEG is also very good). Then let it run to convert the input files, producing a new set of output files.

You can then import the output files to Final Cut and begin editing.

You can also see why editing 24p is viewed as somewhat difficult!

Update Fall 2012

Since this post was originally written, another popular solution has emerged called Neo Scene which converts videos to the Cineform codec (now owned by GoPro). Neo Scene converts your AVCHD into the Cineform codec – files do become much larger but editing becomes much quicker and smoother. The Cineform codec is better suited for editing than is AVCHD and many editing programs can play Cineform coded video in real time, smoothly.

I do not – yet – own this product but have used the trial version and have used the free GoPro Studio (which also uses Cineform but does not support so many cameras). Cineform really works.

Cineform can also handled 24p files embedded in a 60i video stream. Versions are available for both Windows and Mac, and based on my experiments on Windows – Cineform coded files work fine in Sony Vegas Movie Studio 11 and in Magix Movie Edit Pro latest versions.

Converting Camera Video Files Direct to MP4 Format

Plug in your camera and copy the files from the camera to your hard disk. (You can also use iMovie’s Archive feature to do this for you).

Then, run the HandBrake program. It can read AVCHD files and convert directly to MP4 files. HandBrake is quite fast and can be configured to re-size your images to 1280×720, as well as de-interlacing (if you did not shoot in progressive). HandBrake is probably the fastest (and FREE!) utility for converting your camera files direct to MP4 files for viewing XBox360’s, Apple TV etc.

Toast 10 can also do the AVCHD to MP4 conversion in one step.

Cameras, Editing, Techniques

Working with AVCHD video files

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For those accustomed to working with miniDV standard definition video tapes or the HDV 1440×1080 high definition format, the switch to AVCHD may prove challenging from an editing perspective.

“miniDV” and HDV formatted video can be edited directly on most computers with the caveat that editing HDV can take 4 to 5 times longer than mini-DV simply because there are a lot more bits to manipulate for the high definition video. For editing HDV and AVCHD you definitely want at least a dual processor (or dual core) and a minimum of 1 GB RAM (2 or more recommended).

mini-DV records video and audio at a rate of about 25 Mbps. Each video frame is compressed and then stored on the tape, individually using MPEG1 compression.

Summary

  • miniDV image size is 720×480. Data rate is 25 mbps.
  • HDV image size is either 1280×720 (few cameras use this) or 1440×1080. To display an HDV image on a 1920×1080 display, the image is stretched horizontally by 33%. Data rate is 19.7 Mbps (1280×720) or 25 Mbps.
  • AVCHD image sizes are 1280×720, 1440×1080 or 1920×1080 – with a wide variety of data rates from as low as 5 Mbps up to 24 Mbps.

HDV

HDV records video and audio also at a rate of about 25 Mbps. To record a much more detailed image, HDV uses a  compression scheme based on MPEG2. Unlike miniDV, which stores each individual compressed frame, HDV stores a compressed full frame, and then follows that with 14 frames recording only the changes from the first frame.  Since the HDV codec only stores a full frame once every 15 frames, it can do a remarkable job of compressing a 5x larger image into the same space as standard definition recording. (There is also a 19.7 Mbps HDV version for the 1280×720 image size – however, there are few if any any consumer video cameras that record in 1280×720 mode on HDV so we will ignore that.)

The 15 frame sequence is known as a “group of pictures” or GOP. There is also a version with a 7 frame GOP.  While HDV works very well, a major disadvantage is that a single tape drop out will typically ruin up to a full 15 frames – or 1/2 second of video. In the older standard definition encoding, a single dropout killed one frame or 1/30th of a second and no one noticed. With HDV, everyone notices a tape dropout!

AVCHD

AVCHD uses a version of MPEG4 encoding (H.264 or MPEG4 Level 10) that is twice as efficient as MPEG2. That means a 15 Mbps AVCHD encoding is roughly equivalent to a 30 MBps HDV recording (if such a thing existed). However, AVCHD can support multiple image sizes up to the full 1920×1080 HD resolution – plus 1440×1080 and 1280×720.. A 1920×1080 image requires 33% more bits than does a 1440×1080 image.

Most AVCHD based cameras record to Flash memory, and some to hard disk memory. Tape dropouts are then a “thing of the past”. This is a major plus for AVCHD. (Note – you can buy an expensive add on that will record HDV direct from the camera to hard disk to avoid tape drop outs – but these are expensive!) The major negative of AVCHD is that editing is very time consuming or requires huge disk space. And while tape dropouts are gone, you can still get corrupted file problems on the storage media (it happens to everyone eventually).

Editing AVCHD

Editing standard definition video is straightforward since the original video contains each and every frame. Editing HDV and AVCHD is more complicated because the original video does not contain each frame. Further, AVCHD uses a complex encoding scheme that takes a lot more processor time to encode – and decode. Consequently, no matter how you slice it, AVCHD can take longer to edit.

At this time, there are very few editors available that can edit AVCHD files directly (Sony Vegas being a notable exception that can edit AVCHD). Thus, most solutions require that the AVCHD files be converted to an editable format.

On the Mac, the easiest solution is to connect your camera and let iMovie (or Final Cut Express 4 or Final Cut Pro 6) automatically import and convert the AVCHD format files to the Apple Intermediate Codec (AIC) or ProRes 422 codec format. However, converted files expand by 3 to 5 times larger than the original! Where as an hour of HDV or SD video might be less than 13 GB, an hour of AVCHD might be 49 GB! Fortunately, hard disks are now cheap.

So the disadvantage is disk space – but the advantage is very fast editing.  If you have an older version of Final Cut Express (e.g. HD or 3.5) or Final Cut Pro (e.g. 5), you can use iMovie as your importer and then directly import the resulting converted files in to Final Cut (or just edit in iMovie if you want). If you set your time line sequence to AIC codec in Final Cut, you can import and edit all the files directly without a “rendering” step.

On Windows, the most straight forward solution is to use Sony Vegas – or the newest version of Adobe Premiere Pro CS4 or Premiere Elements 7 (update: or Magix Movie Edit Pro or Pinnacle Systems video editor). The advantage to direct AVCHD editing is very fast access to the files – the disadvantage is that each transition (dissolve for example) or title may require that the AVCHD be decoded into individual frames at edit or render time. So the time issue just gets pushed to a different part of the editing workflow.

Other wise, you’ll need to buy an application like VoltaicHD[1], which will convert the AVCHD files to AVI files that can then be imported to other editors (but which may require a rendering step in the editor). The files will also become a lot larger after conversion.

Some AVCHD capture programs enable you to view thumbnail clips of the original AVCHD that is still on the camera – and then select to import only the clips you want to work with (iMovie, Roxio Toast 10). Many also provide a way to quickly copy the compressed AVCHD files and archive those files – either by writing them to hard disk or, for some, burning to a DVD data disc for long term storage.

UPDATE TO NEXT PARAGRAPH: ROXIO TOAST 10 IS DEFECTIVE AND IS UNABLE TO CORRECTLY PROCESS AVCHD FILES. IT WILL PRODUCE FILES WITH UNSYNCHRONIZED AUDIO AND VIDEO.

Another method that works on the Mac is to use Roxio’s Toast 10 software. It can read AVCHD files from your camera and convert them to any format – including HDV or NTSC DV for subsequent editing. Obviously, if you decode a compressed AVCHD file and then re-encode into another compressed format like HDV, you will lose a tiny bit of image quality. Depending on the original source material, most people won’t notice.

Finally, there is the issue of dealing with 24p – or 24 frames per second mode. Depending on the camera and the editing software used, you may have to perform an “inverse telecine” operation on the original 24p video prior to editing. See footnote 2.

Update Fall 2012

Since this post was originally written, another popular solution has emerged called Neo Scene which converts videos to the Cineform codec (now owned by GoPro). Neo Scene converts your AVCHD into the Cineform codec – files do become much larger but editing becomes much quicker and smoother. The Cineform codec is better suited for editing than is AVCHD and many editing programs can play Cineform coded video in real time, smoothly.

I do not – yet – own this product but have used the trial version and have used the free GoPro Studio (which also uses Cineform but does not support so many cameras). Cineform really works.

Cineform can also handled 24p files embedded in a 60i video stream. Versions are available for both Windows and Mac, and based on my experiments on Windows – Cineform coded files work fine in Sony Vegas Movie Studio 11 and in Magix Movie Edit Pro latest versions.

Working with 1920×1080 AVCHD

On the Mac, if you are using iMovie as your editor, you need to be aware that the AIC codec only stores 1440×1080 images. So when you import your 1920×1080 images, they are re sized to 1440×1080 and then stored in the AIC format.

Does it matter?

Reading online forums, I see many people are focused on their 1920×1080 pixel resolution of their new Flash-based camera – but neglect that many consumer lenses cannot deliver the full resolution anyway. And after transcoding and editing, they then generally output their final production to 1280×720 video for online upload, or display via AppleTV, Sony PS3 or XBox 360. Or they burn a standard definnition DVD at 720×480.

What that means – 1920×1080 may not be as important as you think. Yes, 1920×1080 recorded on your camera, and then hooked up to an HDTV via an HDMI cable will look super! But only if you play back from the camera.

If you edit, transcode and ship as 1280×720 or standard DVD, no one will be able to tell the difference if you recorded your original in 1920×1080 or 1440×1080 or 1280×720.

What is more important to image quality is the person behind the camera making good decisions about what to photograph and how to photograph – and using a tripod of monopod wherever possible for steady images. Avoid excessive fast pans and fast zooms – which can make your highly compressed media turn to mush trying to deal with so much rapid motion.

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Notes

[1] There are a bunch of Windows-based programs that claim to convert AVCHD to other formats. Oddly, the programs are nearly identical except for minor changes to their user interface. Most seemed to be based on the freely available ffmpeg program (but which does not support AVCHD) with some AVCHD decoder added on. The programs are so similar, that I suspect they are all distributed by the same organization under different names (but all priced at $35) as some sort of market strategy. Who knows? Anyway, VoltaicHD is its own program and not part of the mass distribution of similar programs. I’ve run a demo of VoltaicHD and it worked fine.

[2] Working with 24p. Some of the newer cameras offer 24 frame per second shooting mode. Some, like Canon’s HG10, HG20, HV20/HV30 stuff the 24 frames into a 60-interlaced fields sequence using a technique known as 2:3 pulldown (which I will not try to explain here). To edit this type of 24p, you must first pre-process the video (which otherwise resembles normal 60i video) to remove the pulldown frames prior to editing. The VoltaicHD program has an option to do this automatically during the transcoding from AVCHD step – which will save you time in the longer run. Otherwise, for example, I have imported using iMovie, but then run the imported videos through the JES Deinterlacer using it’s pulldown removal option (also known as “inverse telecine”), which adds another step and more disk space to the issue of shooting in 24p!