New Image Compressor Components

QuickTime 3 includes a compressor component and a decompressor component for DV video. These components are described in the following sections.

DV Image Compressor Component

The DV image compressor component makes it possible to compress QuickTime video data into DV format. It is invoked automatically by the Image Compression Manager when an application requests output of type kDVCNTSCCodecType for NTSC DV data or kDVCPALCodecType for PAL DV data.

When creating NTSC video, the DV image compressor component generates 720 X 480 frames. When creating PAL video, it generates 720 X 576 frames.

Note: Many DV devices use IEEE 1394 (FireWire) serial connections for input/output operations. QuickTime supports compression and decompression of DV data, but it does not include support for FireWire communication. You need additional software to communicate with DV devices.

DV Image Decompressor Component

The DV image decompressor component makes it possible to decompress DV video data. It is invoked automatically by the Image Compression Manager when an application specifies input of type kDVCNTSCCodecType for NTSC DV data or kDVCPALCodecType for PAL DV data.

There are two quality modes for DV decompression:

In the low-quality mode, which is the default, the DV image decompressor component generates a 1/4-screen image. When operating in this mode, the component uses approximately 25% of the video data in the DV stream and correspondingly fewer system resources.
In the high-quality mode, the component processes all of the video data in the DV stream. Applications can specify the high-quality modem by calling the SetMediaPlayHints function with the hintsHighQuality flag set.

When a computer includes a video display adapter that performs YUV decompression in hardware, the DV image decompressor can use a YUV decompressor component written to use the hardware decompression capabilities in place of the software YUV decompressor in QuickTime, resulting in even higher performance.