DM6446 Codecs

H264 Encoder

The DM6446 H264 Encoder implements the Base Profile. Resolutions up to PAL (720x576)

H264 BP Encoder v1.1x vs. v1.2x

The H264_E BP v1.2x provides several new features. Here are some of them (for complete list please read the release notes:

 1) intra4x4 in I and P frames
 2) access to motion vectors and SAD information for all macro blocks
 3) run time change in bit-rate, frame rate and resolution

The encoder has two configurations, HIGH_QUALITY and HIGH_SPEED, that hardcode some of the extended parameters to achieve best video quality and best processing speed.

The intra4x4 support is part of the HIGH_QUALITY configuration and increases significantly the CPU load. It should be used only for smaller resolution. With D1 resolution, the performance will not be real time. The HIGH_SPEED configuration disables the intra4x4 support, however the CPU load is still a little bit higher than the HIGH_SPEED configuration in the v1.1x. Indeed, the support for the new features has increased the code size and impacts the cache performance.

If an application does not require the new features supported by v1.2x, than it is recommended to use v1.13.

FAQ:DM6446 H264 BP Encoder

Are Intra 16x16 prediction modes supported?

Yes, intra16x16 is used by default, intra4x4 is used supported only in v1.20.

What motion estimation partition sizes are supported?

16x16

Is the ME search range configurable?

The ME search range is not user configurable, but supports unrestricted motion vector search +/-32

Is fractional frame rate supported?

Yes, it is supported till the accuracy of 0.25

How many reference frames are used?

One ( Base Profile)

What input memory configurations are supported – e.g. can the pitch != width?

Pitch != width is not supported Width/Height can be arbitrary – do not have to be multiple of 16

What is the min width and height supported?

Min resolution validated is qcif.

Can the decoder run at very low frames rates, such as 5 fps or 1 fps?

The frame rata can be controlled at the application level. Frames can be dropped to achieve 5 or 1 fps. The encoded output will depend on what the bit-budget is for 1 second.