Stereoscopic Formats

Stereoscopic pair consist of two slightly different images of the same size captured from for left and right eyes (e.g. from two camera positions). This pair can be stored in various ways in the file:

• Mono - no stereoscopic information, only single view is provided
• Dual Stream - each view is stored in independent stream or file
• Cross-eyed, Parallel pair - two images packed horizontally, also known as Side-by-Side
• Over/Under - two images packed vertically, also known as Top-Bottom
• Interlaced - row interleaved (obsolete)
• Anaglyph - image stored for glasses with color filters (obsolete)
• Frame-sequential - views (frames) interleaved in time (first frame Left view, second frame Right view and so on)
• 2x720p in 1080p tiled - special layout used by some TV broadcasters in Europe

Program will be able to show image properly only when stereoscopic format has been properly selected. sView is able to determine stereoscopic format using:

• Multiple streams (*.mpo, *.mkv, *.wmv). Two image / video streams of the same size are automatically detected as stereoscopic pair with Left view in the first stream.
• JPEG image containing JPS marker (VRex extension). JPS marker defines stereoscopic format.
• PNG image containing sTER chunk (Extensions to the PNG). Only parallel pair with views order can be defined by sTER indicator.
• WMV metadata (*.wmv). The following metadata fields will be interpreted by sView:
  • StereoscopicLayout defining one of layouts (SideBySideRF, SideBySideLF, OverUnderLT, OverUnderRT)
  • StereoscopicHalfHeight and StereoscopicHalfWidth defining anamorphic video
  • StereoscopicHorizontalParallax defining parallax in pixels
• MKV metadata (*.mkv, *mkv3d). Matroska specification includes dedicated fields defining stereoscopic layout (StereoMode). FFmpeg library converts this data in form of stream metadata with name STEREO_MODE (with values mono, right_left, left_right, bottom_top, top_bottom, row_interleaved_rl, row_interleaved_lr, block_lr, block_rl, anaglyph_cyan_red, anaglyph_green_magenta). Note that detection code in sView is generalized and specified metadata tags will be read from any video file (not only *.mkv).
• h264 SEI messages (per frame side data, *.mp4, *.mkv). Some codecs stores stereoscopic identification data at every frame. This technically allows to switch from mono to stereo3d within the same stream. FFmpeg provides this information in form of AVStereo3D structure - thus sView will be able to read this information for all decoders in FFmpeg supporting this feature.
• File extension (*.pns, *.jps). Image files with extensions *.pns (PNG file) and *.jps (JPEG file) will be interpreted as stereoscopic pair in Side-by-side format with Right view first (cross-eyed).
• File name. sView supports the following name convention for stereoscopic format identification:
  • half-ou, -hou, -abq define anamorphic Over/Under pair
  • half-sbs, -hsbs, -lrq, -rlq define anamorphic Side-by-side pair
  • -ba, -ab define Over/Under pair
  • -sbs, -lr, -rl define Side-by-side pair

Anamorphic stereo pair with Side-by-side and Over/Under layout is a special format introduced for compatibility with build-in TV players and existing hardware players without HDMI 1.4a+ support. Video stored in this format has broken pixel proportions - it identifies itself as normal 16:9 video with 1080p HD resolution (1920x1080). Both are important - old hardware players have been unable to decode videos of greater side, and 16:9 proportions allow transferring video image through HDMI without extra scaling or cropping which should be normally applied. So in general this format has been created as a temporary hack entrenched for much longer time than expected…

Normally files should contain appropriate stereoscopic metadata to be properly displayed by players without user involvement. Unfortunately, many files still created without this information requiring manual configuration by user.

If your file has been opened wrong you should try to change “source stereo format”. In most cases this is just layout which defines how left and right views are stored in single frame. At first step you should select “Mono” format to see the original frame.

	Side-by-side Left-eye and right-eye views are stored as a whole horizontally. Since views order is not standardized you should try both "Cross-eyed" (Right view at left side, Left view at right side) and "Parallel Pair". If image looks correctly but you experience discomfort - you have probably chosen wrong views order. Notice that images with extensions "JPS" (JPEG stereo) and "PNS" (PNG stereo) are expected in "Cross-eyed" order whilst movies and other images might be stored in any order.
	Over/Under Left-eye and right-eye views are stored as wholes and placed vertically. If image looks correctly but you experience discomfort - you have probably chosen wrong views order. This format is commonly used in videos.
	Interlaced In this format left and right views are interlaced line by line: each line correspond to each view vertically in turn. In expressive stereo-volume, this picture in the source (means played not in stereo-viewer) seen like with "noise".
	Anaglyph This format comes specially for viewing devices - color glasses. Views are stored in MIX (meaning each pixel stores both views), separation provided by color filters in glasses (most used and most old - red-blue filters). This format is easy-to-recognize by color noise. Unfortunately, materials stored in this format are unusable by most devices (not color-glasses) due to serious color losses.