The Infoframe of HDMI

Link: http://blog.csdn.net/yyao1024/article/details/6398727

Avi/audio infoframe belong to a secondary data category. A Infoframe package can only carry a infoframe. Also, depending on the HDMI specification, the size is limited to 30 bytes plus a check and (CheckSum) byte.

Whether the image is YCbCr or RGB, it is very important to transmit it, at least every two frames of the image to pass an AVI infoframe. HDMI source uses it to tell HDMI sink about the various characteristics of the image to be transmitted, such as: Encoding (RGB/YCBCR), scanning mode (Overscan/underscan), Zoom (16:9/4:3), pixel repetition rate, and so on.

HDMI in the format is based on the position of the TV to do, and is directly from the Eia/cea-861-b "A DTV profile for the uncompressed high Speed Digital interfaces" standard reference. Eia/cea-861-b has a format of up to 34, and if you add some minor changes such as pixel repetition (Pixel repetition), there are 348 of them. As a result, many of the fields are from eia/cea-861b, and the details are quite complicated.

Description of the Infoframe

The above figure Avi Infoframe Packaging Header (Packet header) and packaging content (Packet content) format, simple grasp a focus, AVI Infoframe contains information is to achieve and reach the display mode automation ( Display Mode Automation) a method or mechanism for planning. Of course, all the emphasis is in the field of packaging.

Y0, Y1:RGB, or YCbCr indicator. Is the coding of the color and the sampling method (color Encoding & sampling Methods).

A0:active (format) information present is a banner that indicates whether the R0~R3 is valid, and R0~R3 is the active format Aspect Ratio.

Flag that B0, B1:bar info data is valid.

S0, S1:scan information. Information about the security scope. For example, full screen (overscan) and non-full screen (Underscan).

C0, C1: Colorimetric method (Colorimetry), ITU bt.601,bt.709 and so on.

M0, M1:picture Aspect Ratio (4:3, 16:9). The EIA/CEA-861-B standard section 2.4 defines the vocabulary of the picture Aspect ratio as the aspect ratio of the image transmitted over the uncompressed digital interface.

R0~R3 is the active Format Aspect Ratio.

Vic0~vic6:video Format identification Code.

Pr0~pr3:pixel repetition Factor. Relates to the issue of double clocking & Pixel repetition. For example, video formats with speeds below 25HMz (such as 480i in NTSC are only 13.5MHz) can be transmitted using the mechanism of pixel repetition (Pixel repetition).

SC1, Sc0:non-uniform picture scaling, is morph mode.

The packaged content of AVI Infoframe also includes:

Etb:line number of end of the top bar.

Sbb:line number of start of bottom bar.

Elb:pixel number of end of the left bar.

Srb:pixel number of start of right bar.

AVI Infoframe content not to understand, you can use a comparative image of the analogy to explain, some people make the format of the film will have a variety of tricks, and its content is not necessarily with the consumer's TV in the aspect ratio (Aspect Ratio), so even if you have a very intelligent TV, The only way to make an optimal display of the content image is to understand the image condition that is received, which is what Avi Infoframe to do.

The source device of the HDMI interface uses the IEC 60958 Channel status, IEC 61937 Burst info, and Audio infoframe to express the characteristics of the active audio string, Audio Infoframe transmission is any point in time when the data island package can be loaded.

It should be noted that many of the fields in the package can be set to zero, indicating that this information has been implied in IEC 60958 Channel status, IEC 61937 Burst info.

CC0 ... Cc2:channel Count.

CT0 ... Ct3:coding Type.

SS0 ... Ss1:sample Size.

SF0 ... SF2 Sample Frequency. For L-PCM and compressed audio, these bits must be zero. For a Super Audio CD, the bit setting must be [0,1,0], representing a 2.8224M sample (64x44.1khz).

CA0 ... Ca7:channel/speaker allocation. These bits are not valid for compressed audio.

LSV0 ... Lsv3:level Shift Value.

Dm_inh:down-mix inhibit.

The additional data transmitted by the

Audio Infoframe contains the configuration of the L-PCM loudspeaker horn and the correction of the blending volume (Down-mix Volume) adjustment.