Stereo Video Production : Export

Scott Lawrence (formerly with Vuzix Corp.)
yorgle@gmail.com

April 2008


Introduction
Hardware
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Exporting / Transcoding The Content

6.0: Table Of Contents

NOTICE: The following directions are out of date. The HandBrake settings might be incorrect. Furthermore, Vuzix Eyewear now support a side-by-side format for 3D which preserves the picture quality much more easily.

6.1: Overview

The video encoding must preserve discrete video information in both fields in order to prevent ghosting of the imagery on playback. However, it is difficult at best to preserve field data for lower bitrate movies in the MPEG formats that we must use for distribution for common playback devices.

We've done a fair bit of testing of different content at different bitrates. What follows is the resulting knowledge from all of our testing, as well as the specifications provided by the various playback device manufacturers.

There is no global standard as to which eye should be in which field. 3D Digital Cinemas that use an interlaced video file format will store the left eye in the upper (first) field. For compatibility sake, we recommend doing this as well. We also recommend that all of your content adhere to the same standard across all of your produced media.

6.2: Playback Device Specifications

6.2.1: NTSC SD-DVD

This is probably the easiest format for which to generate high quality 3D stereoscopic content. Your content needs to mastered for DVD as a full-frame(4:3) NTSC 480i video. The fields must remain as independent as possible during the transcoding process, so that the two streams of video remain independent of each other. Some transcoders/resizers will take a full frame, consisting of both fields, and resize them as one complete image, mixing the fields together.

If resizing is necessary due to the source content being of a higher or lower resolution, then care must be taken to make sure that the two eyes are either scaled independently of each other, or that the independence of the fields is preserved. We recommend doing any resizing as early in the workflow as possible; before applying the 3D interlacing if possible.

  • DVD Video Data: NTSC 4:3 MPEG2, 720x480i
  • DVD Video Bitrate: 3 to 9.8 Mbps adaptive
  • DVD Video Suggestions: Any standard supported bitrate 90-150 minute works well.
  • DVD Audio Data: PCM, AAC, etc.

6.2.2: NTSC Apple iPod and iPhone

Apple has accounted for the limited bitrate capability of iPod devices by providing H.264 based compression which looks better than MPEG-4 at low bitrates. Our research has shown that this fails to preserve field-based content, so it is not useful for field-sequential stereoscopic video.

We recommend the highest bitrate you can comfortably distribute. A 5 minute movie at 1 Mbps takes half the space of a 2 Mbps movie, but as described earlier, that extra bandwidth is critical to reproduce the two independent eyes of imagery. We have not had any good results going below 1.75 Mbps; imagery gets very blocky, colors get mixed between eyes.

  • iPod Video Data: NTSC 4:3, MPEG4, 640x480i "simple" ISMA profile
  • iPod Video Bitrate: Up to 2.5 Mbps supported
  • iPod Video Suggestions: 2.2 Mbps to 2.4 Mbps, if possible
  • iPod Audio Data: AAC-LC up to 160 Kbps, 48kHz stereo

Please refer to Apple documentation for full details about producing MPEG4 video content for use with the iPod and iPhone. We suggest transcoding your content to a few bitrates to see which is the lowest acceptable.

  • IWEAR_3D - Left dominant 3D
  • IWEAR_3DL - Left dominant 3D
  • IWEAR_3DR - Right dominant 3D

The end user will need to make sure that their iPod is set for "NTSC" and enable "TV Output". If these steps are not taken, then the image may appear on the external viewing device either as a flickery, desaturated mess, or not at all.

6.3: Software

For the sake of brevity, only Macintosh tools will be discussed in this documentation.

6.3.1: Macintosh - Compressor - DVD


Export for DVD

Stereo 3D content should be exported from Final Cut through Compressor from Apple. As explained previously, all of the built-in DVD video settings should be adequate to faithfully reproduce the stereo 3D effect properly. That is to say that any of the 90, 120, and 150 minute NTSC 4:3 presets work fine.

6.3.2: Macintosh - Compressor - iPod


Export for iPod

We have not had very good luck exporting footage through compressor using its built-in iPod presets. The above video shows how to create a new preset for exporting field-sequential video for iPod.

An alternate method is of course to use the above procedure and export your video to DVD, then use a DVD extraction tool like "HandBrake" to read the DVD back in, and generate the iPod format videos. We have had very good results using this tool to do these kinds of things. See the below "Transcoding" section for more information on this subject.

6.4: Transcoding

Transcoding your video data from one format to another can be tricky, but if you're careful you can have some excellent results. Always remember to stay within the parameters for the target device as described above.

NOTE: Extracting video data from copy protected or store purchased DVDs or any other copy protected medium is an illegal action, and can result in legal action being taken against you. Any discussion on this matter in this document applies to DVD content that you have produced yourself, is on non-copy protected media, and you posess the legal rights to do so.

6.4.1: Macintosh - HandBrake

Handbrake is useful for taking your legal, unprotected DVD content and generating iPod-ready footage from it. Do note however, that you will need to edit the "Composer" tag, as described above in order to work properly with the IP230 devices.

The recommended settings for HandBrake for producing field-sequential stereo-capable iPod files is as follows.

  1. Select the "iPod High-Res" preset.
  2. Output Settings Format: reselect "MP4 File"
  3. Codecs: MPEG-4 Video / AAC Audio
  4. Video Tab: 2-Pass Encoding
  5. Average bitrate (kbps): try values between 1500 and 2300. We suggest 2200.
  6. Click "Picture Settings"
  7. Keep Aspect Ratio (note that the width and height may change when this is selected)
  8. Width: around 640 is best
  9. Height: MUST be 480
  10. Crop: Custom: make sure the top and bottom values are 0s.
  11. Detelecine: Does not affect 3D
  12. Deinterlace: None
  13. Denoise: Does not affect 3D
  14. Click "Close"
  15. In the presets drawer, click on the "+" button at the bottom
  16. Name this preset "DVD for 3D Eyewear"
  17. Select "Current" for Picture Settings
  18. Click "Add"

You can now use this preset whenever you have 3D Stereo DVD content to convert to iPod-displayable content.

Any sort of vertical cropping of the image, or otherwise producing a non 480 line output image will result in damage to the 3D reproduction process.

6.4.2: Visual Hub

Visual Hub is a tool that takes in video files in just about any video format, and exports in just about any other video format. Do note however, that you will need to edit the "Composer" tag as described above in order to work properly with the IP230 devices.

The recommended settings for VisualHub for producing field-sequential stereo-capable iPod files is as follows.

  1. Select "iTunes"
  2. Optimize for: "iPod (5G)"
  3. Quality: "Go Nuts"
  4. Deselect "H.264 Encoding" if it is selected
  5. Select "Add to iTunes"

You may also want to do the following if its results are not acceptable

  1. Select "MP4"
  2. Quality: "Go Nuts"
  3. Deselect "320 Pixels Wide" if it is selected
  4. Deselect "H.264 Encoding" if it is selected
  5. Click "Advanced..."
  6. In the Advanced Settings, set the Width to 640
  7. In the Advanced Settings, set the Height to 480
  8. In the Advanced Settings, select "Two Pass"

You may want to convert your video content using both sets of settings and distribute the one that has the better quality output with your content.

6.4.3: Windows - Total Video Converter

We have had good results converting video formats for iPod use, with Total Video Converter. It is able to reproduce stereo 3D from the resulting iPod movies without problems.

We recommend that you use as high of a bitrate as possible. Refer to the table earlier in this documentation for the limits and format of iPod file formats.


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DISCLAIMER:
This author of this page was happily employed by the Vuzix Corporation. All hacks and modifications are acknowledged but not advised by Vuzix. Do modifications at your own risk. No warranty is expressed or implied. That said, the content described above is known to have worked for me and is correct to the best of my knowledge. Any questions about the content, procedures, or information should be directed to me at the email address given at the top of the page.