SoundCheck Display |
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Sound format: From the main window it is possible to select the sample rate, number of channels and the number of bits per sample. See the page on digital sound for an explanation of these terms. Different sound cards support different sound formats and many cards will not support the highest sample rate. Selecting high sample rates, stereo input and 16bit samples will all increase the data rate. Only the fastest computers will be able to process high data rates in real time. You may find that you need to lower the sample rate or frame rate (see below) in order for your computer to keep up with the flow of data. Data rate: This part of the window shows the requested, actual and average data rates. The data rate is the number of bytes per second that are transferred either to or from the sound card. The requested data rate is directly related to the sound format selected. The actual data rate is the data rate that occurred during the last half a second. As data is transferred in blocks of 512 samples from the sound card, it is normal that the actual rate varies slightly from the requested rate. The average rate is the average data rate since the recording or playback was started. After a few seconds this number should converge to the requested data rate. If the actual or average data rates are significantly below the requested rate, then there may be a problem with your sound card or, more likely, your computer is not fast enough to maintain the requested transfer rate. Typically the deviation between the average rate and the requested rate should be well under 1%. Graph settings: The graph type and refresh rate can be selected here. The two graph types available are the Waveform graph and the Spectrum graph. Both are capable of processing and displaying data in real time or at a reduced refresh rate. The Waveform graph plots the sound wave as each block of data arrives from the sound card. This operates in a similar manner to a traditional oscilloscope. The horizontal axis represents time and the vertical axis represents amplitude. When stereo is in use, channel 1 is drawn in green and channel two is drawn in red. Note that when the input is the same on both channels, the mixture of red and green on the display can look a little strange. The trigger toggle option is only applicable when in waveform view. When this mode is turned on the waveform graph will always begin drawing the wave at a point where the signal has crossed from a positive value to a negative one. Record and playback buffers: The size of the buffer and the current contents of the buffer can be seen in this part of the window. The size of the buffer determines how much sound can be recorded and played back. A buffer of equal size is required for recording and playback. Thus setting a buffer size of 10MB requires the computer to have 20MB of free RAM.
Waveform View: Spectrum View:
A vertical and horizontal slider bar, at the left and the bottom of the view window respectively, allow a limited range of zooming on the graphs. Horizontal zoom controls the amount of samples that are displayed on each page of the graph. At slower sample rates, and high horizontal zoom, the ‘stepping’ of the graph data becomes more apparent. Vertical zoom controls the ratio the amplitude is plotted against on the graph. The current range of data view (as per the x-axis) is displayed in the extra information located in the top left corner of the graph. Display Settings: Clicking View -> Display settings brings up a dialog which allows control over various information and features displayed in the main view window. Show Grid – Toggles the grid on or off. |