Here's something I posted in another thread here about HDMI cables and video. It will save some of you the trouble of looking it up....
HDMI uses TMDS (Transition Minimized Differential Signaling) to send data. In short, each 8bit data value is encoded into a 10bit value before it is sent over the "wire".
The encoding is done to minimize the 0->1 and 1->0 transitions: The encoder chooses between XOR and XNOR by determining which will result in the fewest transitions; the ninth bit is added to show which was used. In the second stage, the first eight bits are optionally inverted to even out the balance of ones and zeros and therefore the sustained average DC level. The tenth bit is added to indicate whether this inversion took place.
In order for a cable to uniformly change a video stream that looks "better" or "worse", the random bit changes of every 10bit value would have to somehow decode to uniform changes in the resulting 8bit value. Chances of this happening - ZERO.
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Sending PCM over HDMI is somewhat different. The audio info is sent in between the video frames (blanking interval, IIRC) and is has error correction (unlike video). When just audio is sent, video frames still have to be used. However, the clocking is sent over a separate "wire" of the cable so recovering the clock on the target end and "synchronizing" with the incoming audio data could be prone to jitter.
larry
HDMI uses TMDS (Transition Minimized Differential Signaling) to send data. In short, each 8bit data value is encoded into a 10bit value before it is sent over the "wire".
The encoding is done to minimize the 0->1 and 1->0 transitions: The encoder chooses between XOR and XNOR by determining which will result in the fewest transitions; the ninth bit is added to show which was used. In the second stage, the first eight bits are optionally inverted to even out the balance of ones and zeros and therefore the sustained average DC level. The tenth bit is added to indicate whether this inversion took place.
In order for a cable to uniformly change a video stream that looks "better" or "worse", the random bit changes of every 10bit value would have to somehow decode to uniform changes in the resulting 8bit value. Chances of this happening - ZERO.
---------------------
Sending PCM over HDMI is somewhat different. The audio info is sent in between the video frames (blanking interval, IIRC) and is has error correction (unlike video). When just audio is sent, video frames still have to be used. However, the clocking is sent over a separate "wire" of the cable so recovering the clock on the target end and "synchronizing" with the incoming audio data could be prone to jitter.
larry