TI rolls DaVinci for HD transcoding

Houston, TX — Texas Instruments (TI) has announced the newest member of its DaVinci family of video-processing SoCs, the TMS320DM6467. The device, priced at $35.95 in 50K volumes, targets video transcoding in products such as set-top boxes, media gateways, and digital media adapters. The TMS320DM6467 can simultaneously encode and decode multi-format HD video at resolutions up to H.264 HP@L4 (1080p 30fps, 1080i 60fps, or 720p 60fps).

The device, shown in Figure 1, features an ARM9 running at 300 MHz, a C64x+ running at 600 MHz, and a host of video coprocessors. The biggest performance boost for transcoding applications comes from the HD Video/Imaging Coprocessor (VICP), which pairs an encoder coprocessor with a decoder coprocessor. (Previous DaVinci parts had only a single encoder coprocessor.) The VICP gives the DM6467 enough horsepower for "brute force" transcoding, that is, fully decoding a stream in one format and simultaneously re-encoding in another.

(Click to enlarge)
Figure 1. High-level block diagram of the DM6467.

For more efficient transcoding, the encode and decode coprocessors can communicate via a shared memory. This allows processing shortcuts such as reuse of motion vectors. Reusing motion vectors greatly simplifies motion estimation, which is the most processing-intensive step in video encoding.

The TMS320DM6467 also provides a Video Data Conversion Engine which contains coprocessors for chroma sampling, resizing, and on-screen display. These are similar to coprocessors found in the 'Video Processing Subsystem' (VPSS) in other DaVinci parts. One notable difference is the resizer. In other DaVinci parts the resizer can scale up to 4x or down to 1/4x. Since transcoders almost always leave resolution the same or scale it down, the resizer has been converted to strictly a downscaler that scales down to 1/8x. This feature is particularly useful when transcoding video for mobile devices with small resolutions.

To get video in and out of the chip, the TMS320DM6467 has two 8-bit BT.656 inputs and outputs that can be reconfigured into a single 16-bit BT input and output. Video data can also be streamed in and out via PCI or gigabit Ethernet interfaces.

As for software, the DM6467 comes with the same comprehensive set of OSs and audio/video codecs offered on previous DaVinci parts. In addition, TI has included an MPEG-2 to H.264 transcoder. This transcoder does a "brute force" decode of MPEG-2 and re-encode with H.264. The company reports that more intelligent "tightly coupled" transcoders are under development by TI 3rd-party partners.

The DM6467 is currently sampling and priced at $35.95 in 50K volumes. The DVEVM is scheduled to begin shipping in 1Q08. For more info visit www.ti.com.

– By Seth Benton (travelingseth@yahoo.com), analyst at Cabral Consulting, and Kenton Williston (kentonwilliston@yahoo.com), site editor of DSP DesignLine (www.DSPDesignLine.com ) and president of Cabral Consulting.

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