Editing Header/Payload Demux

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===Symbols, Items and Item Sizes===
 
===Symbols, Items and Item Sizes===
  
To generically and transparently handle different kinds of modulations, including OFDM, this block distinguishes between symbols and items.
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To generically and transparently handle different kinds of modulations, including OFDM, this block distinguises between symbols and items.
  
 
Items are what are consumed at the input. Anything that uses complex samples will therefore use an itemsize of <code>sizeof(gr_complex)</code>. Symbols are a way of grouping items. In OFDM, we usually don't care about individual samples, but we do care about full OFDM symbols, so we set <code>items_per_symbol</code> to the IFFT / FFT length of the OFDM modulator / demodulator. For single-carrier modulations, this value can be set to the number of samples per symbol, to handle data in number of symbols, or to 1 to handle data in number of samples. If specified, guard_interval items are discarded before every symbol. This is useful for demuxing bursts of OFDM signals.
 
Items are what are consumed at the input. Anything that uses complex samples will therefore use an itemsize of <code>sizeof(gr_complex)</code>. Symbols are a way of grouping items. In OFDM, we usually don't care about individual samples, but we do care about full OFDM symbols, so we set <code>items_per_symbol</code> to the IFFT / FFT length of the OFDM modulator / demodulator. For single-carrier modulations, this value can be set to the number of samples per symbol, to handle data in number of symbols, or to 1 to handle data in number of samples. If specified, guard_interval items are discarded before every symbol. This is useful for demuxing bursts of OFDM signals.
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====Example:====
 
====Example:====
 
PSK-modulated signals, with 4 samples per symbol. Again, itemsize is <code>sizeof(gr_complex)</code> because we're still dealing with complex samples. items_per_symbol is 4, because one item is one sample. <code>guard_interval</code> must be set to 0. The header length is given in number of PSK symbols.
 
PSK-modulated signals, with 4 samples per symbol. Again, itemsize is <code>sizeof(gr_complex)</code> because we're still dealing with complex samples. items_per_symbol is 4, because one item is one sample. <code>guard_interval</code> must be set to 0. The header length is given in number of PSK symbols.
 
 
===Handling timing uncertainty on the trigger===
 
===Handling timing uncertainty on the trigger===
  

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