IMX Format Specifications

IMX, also known as Betacam IMX or MPEG IMX, records SD NTSC and PAL video using high-quality MPEG-2 compression.

Storage Medium

One of the features of the IMX format is that it is not restricted to a single media type. IMX can be recorded on XDCAM, a Sony optical disc format, as well as the IMX tape format.

IMX VTRs bridge the gap between conventional tape decks and modern computer editing systems with the following features:

  • Playback of older video formats such as Betacam SP, Beta SX, and Digital Betacam. These formats can be converted and output to MPEG IMX in real time.

    Note: Not all IMX VTRs support playback and recording of all Betacam formats.

  • IMX digital video file transfer via networking interfaces such as Ethernet and TCP/IP protocols

Video Standard

IMX supports both SD NTSC and SD PAL.

Aspect Ratio

NTSC and PAL IMX both have an aspect ratio of 4:3.

Frame Dimensions, Number of Lines, and Resolution

IMX can store video at two possible resolutions: NTSC (525) and PAL (625). The numbers refer to the number of analog lines of the corresponding video formats. However, many of these analog lines are not used to store picture information. In Final Cut Pro, the following frame dimensions are used:

  • NTSC IMX: 720 pixels per line, 486 lines
  • PAL IMX: 720 pixels per line, 576 lines

In both formats, standard definition rectangular pixels are used, just as with DV, DVD, Digital Betacam, and other SD digital video formats.

Frame Rate

IMX supports NTSC and PAL frame rates of 29.97 fps and 25 fps, respectively.

Scanning Method

IMX supports interlaced recording.

Color Recording Method

IMX records a 4:2:2 Y′CBCR (component) digital video signal. Each sample (pixel) has a resolution of 8 bits.

Data Rate and Video Compression

IMX uses I-frame-only MPEG-2 compression. IMX is a restricted version of MPEG-2 4:2:2 Profile @ ML. The official SMPTE designation is D10, as specified in SMPTE standard 356M.

Three compression ratios are supported:

  • 30 Mbps: 5.6:1 compression
  • 40 Mbps: 4.2:1 compression
  • 50 Mbps: 3.3:1 compression
Audio

IMX supports two audio channel configurations:

  • Four audio channels, sampled at 48 kHz with 24 bits per sample

  • Eight audio channels, sampled at 48 kHz with 16 bits per sample

Timecode

IMX supports 30 and 25 fps timecode.