Whilst many are led to believe that once you have purchased a HDMI cable you should only expect to see high quality audio and video rendering, the truth is that the fidelity at which your media render is played depends on a few other factors as well. Therefore, you should not be alarmed once the display is less then perfect or the audio quality is lacking, but rather analyze the cause why this occurs. So, what can interfere with the fidelity of your media playback?
Firstly, the signal source itself can be at fault. It is true that the HDMI cables work on restoring damaged or missing bit sequences using a bi-way digital data transmission. However, there is still a limit to how much the technology can repair it. Moreover, it often happens that the source of the signal, be it a DVD, Blu-Ray or satellite, does not match the type of display you are using. Of course, assuming that the signal comes in digital form, and there is no analog to digital conversion required, both when the signal is received or transmitted to the display and the hardware is a native digital device, the signal should be error-free. However, this is an ideal situation and does not always occur in practice.
Secondly, the length of the HDMI cable plays a major role on the fidelity of the playback. Considering that the bi-way signal is transmitted in an environment with little control over the impedance, the bounce-back is not always optimal. Consequentially, if the signal is not strong or the stream is missing bits, it will become even more obvious on greater lengths. Moreover, whilst the HDMI cables are advertised as being able to transmit uncompressed streams of data, the end result also depends a great deal on how scaling the image will affect picture quality. This is even more important in the case when the original signal does not match the type of display hardware destination.
In conclusion, whilst it is true that the HDMI technology is quite potent, you should not expect it to perform miracles, especially not under all circumstances. It can, in most cases, render accurate audio and video signals, but you should take into account the aforementioned factors involved in the fidelity of the playback rather than assume the cable you have purchased is of inferior quality. Of course, that does not go to say that you should expect the same performance from both low-priced and more expensive HDMI cables, but rather that you should expect that even the best one may not always produce high-end results.