IPSR-VIDEO Altera, IPSR-VIDEO Datasheet - Page 148

• Manufacturer Part Number: IPSR-VIDEO
• Description: RENEWAL Of IPS-VIDEO
• Manufacturer: Altera
• Series: IP Suitesr

Specifications of IPSR-VIDEO

• Software Application: IP CORE, SUITES
• Supported Families: Arria GX, Cyclone II, HardCopy II, Stratix II
• Features: Common Avalon Streaming (Avalon-St) Interface And Avalon-St Video Protocol
• Core Architecture: FPGA
• Core Sub-architecture: Arria, Cyclone, Stratix
• Rohs Compliant: NA
• Lead Free Status / RoHS Status: na

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Video and Image Processing Suite User Guide
Chroma Resampler
During the mixing of a frame, the Alpha Blending Mixer reads from the background
input for each non-stalled cycle. The Alpha Blending Mixer also reads from the input
ports associated with layers that currently cover the background image. Because of
pipelining, the foreground pixel of layer N is read approximately N active cycles after
the corresponding background pixel has been read. If the output is applying
backpressure or if one input is stalling, the pipeline stalls and the backpressure
propagates to all active inputs. When alpha blending is enabled, one data sample is
read from each alpha port once each time that a whole pixel of data is read from the
corresponding input port.
There is no internal buffering in the Alpha Blending Mixer MegaCore function, so the
delay from input to output is just a few clock cycles and increases linearly with the
number of inputs.
Error Recovery
The Alpha Blending Mixer MegaCore function processes video packets from the
background layer until the end of packet is received. If an endofpacket signal is
received too early for the background layer, the Alpha Blending Mixer enters error
mode and continues writing data until it has reached the end of the current line. The
endofpacket signal is then set with the last pixel sent. If an endofpacket signal is
received early for one of the foreground layers or for one of the alpha layers, the
Alpha Blending Mixer stops pulling data out of the corresponding input and pads the
incomplete frame with undefined samples. If an endofpacket signal is received late
for the background layer, one or more foreground layers, or one or more alpha layers,
the Alpha Blending Mixer enters error mode.
When the Alpha Blending Mixer MegaCore function enters error mode (because of an
early endofpacket for the background layer or a late endofpacket for any layer), it has
to discard data until the endofpacket has been reached for all input layers.
This error recovery process maintains the synchronization between all the inputs and
is started once the output frame is completed. A large number of samples may have to
be discarded during the operation and backpressure can be applied for a long time on
most input layers. Consequently, this error recovery mechanism could trigger an
overflow at the input of the system.
All modes of the Chroma Resampler stall for a few cycles between frames and
between lines. Latency from input to output varies depending on the operation mode
of the Chroma Resampler MegaCore function. The only modes with latency of more
than a few cycles are 4:2:0 to 4:2:2 and 4:2:0 to 4:4:4. These modes have a latency
corresponding to one line of 4:2:0 data.
Because this is a rate-changing function, the quantities of data input and output are
not equal. The Chroma Resampler MegaCore function always outputs the same
number of lines that it inputs. However the number of samples in each line varies
according to the subsampling pattern used.
When not stalled, the Chroma Resampler always processes one sample from the more
fully sampled side on each clock cycle. For example, the subsampled side pauses for
one third of the clock cycles in the 4:2:2 case or half of the clock cycles in the 4:2:0 case.
Chapter 5: Functional Descriptions
January 2011 Altera Corporation
Stall Behavior and Error Recovery