- General info
Terrestrial Sound
In an analogue terrestrial television broadcast, sound information can be coded in a variety of ways. Typical standards for coding sound are:
- AM mono (as used in TV system L and L').
- FM mono (as used in TV system BG and others).
- 2CS (2 carrier sound), FM modulated signals which has two carriers. The second carrier contains either stereo information or a second (dual) sound channel.
- NICAM, a digital sound standard, which can contain mono sound, stereo sound, dual sound or data, which is either related or unrelated to the image. NICAM is accompanied by an AM or FM mono signal.
- BTSC, the US standard for sound, which can be mono or stereo, with an optional SAP (second audio program, always mono).
The sound system should not be confused with the TV system. The latter deals with the location of the sound carriers, the former with the modulation and coding techniques. The sound and TV systems are more or less independent, though in practice certain combinations are fixed (such as AM with system L).
Multichannel Sound
Three methods are popular for encoding sound digitally. They are as follows:
- MPEG x/y.z: ISO's Moving Picture Experts Group came up with this method of encoding audio digitally.
- Dolby Digital DD x/y.z: The Dolby Laboratories of USA designed this method of sound encoding.
- Pulse Code Modulation PCM: It consists of 2 front channels only.
In the above, x is the number of front channels (left, right, center, middle left/right, middle left/right can be supported by MPEG only), y is the number of surround channels (maximum two), z denotes the low frequency signal
- Constants
- Sound System
- int AllowAnalog = 1
- int AllowDigital = 2
- int AllowNicam = 4
- int Allow2CS = 8
- int AllowBTSC = 16
- int AllowEIAJ = 32
- int AllowPCM = 64
- int AllowAC3 = 128
- int AllowMPEG = 256
- int AllowDTS = 512
- Functions/Parameters
- FResult AllowSoundSystem( int winid, int system )
Sets the set of sound standards that the decoder is allowed to detect.
| Parameters
| system | The set of sound standards that the decoder is allowed to detect OR-ed.
|
- FResult GetAllowedSoundSystem( int winid, int * retval )
Returns the set of sound standards supported by the decoder.
| Parameters
| retval | Return value with the set of sound standards supported by the decoder OR-ed.
|
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