# HG changeset patch
# User rlm
# Date 1271185710 14400
# Node ID 6d1ff93e3afab2d18b03ff9caa8d3f1abf5754f2

[svn r1] This is the current draft of out project

diff -r 000000000000 -r 6d1ff93e3afa documents/000402.png
Binary file documents/000402.png has changed
diff -r 000000000000 -r 6d1ff93e3afa documents/AudioProcessing.lyx
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/documents/AudioProcessing.lyx	Tue Apr 13 15:08:30 2010 -0400
@@ -0,0 +1,160 @@
+#LyX 1.6.4 created this file. For more info see http://www.lyx.org/
+\lyxformat 345
+\begin_document
+\begin_header
+\textclass article
+\use_default_options true
+\language english
+\inputencoding auto
+\font_roman default
+\font_sans default
+\font_typewriter default
+\font_default_family default
+\font_sc false
+\font_osf false
+\font_sf_scale 100
+\font_tt_scale 100
+
+\graphics default
+\paperfontsize default
+\use_hyperref false
+\papersize default
+\use_geometry false
+\use_amsmath 1
+\use_esint 1
+\cite_engine basic
+\use_bibtopic false
+\paperorientation portrait
+\secnumdepth 3
+\tocdepth 3
+\paragraph_separation indent
+\defskip medskip
+\quotes_language english
+\papercolumns 1
+\papersides 1
+\paperpagestyle default
+\tracking_changes false
+\output_changes false
+\author "" 
+\end_header
+
+\begin_body
+
+\begin_layout Title
+Multi-Voice Audio Playback
+\end_layout
+
+\begin_layout Author
+Laurel Pardue, Robert McIntyre
+\end_layout
+
+\begin_layout Section*
+Micro-Architecture
+\end_layout
+
+\begin_layout Subsection*
+A quick summary of our system
+\end_layout
+
+\begin_layout Standard
+The audio data (
+\begin_inset Quotes eld
+\end_inset
+
+samples
+\begin_inset Quotes erd
+\end_inset
+
+) start in the memory, but are soon pulled into action by the DMA (direct
+ memory access).
+ The DMA sends the samples to a chain of 0 or more 
+\emph on
+soft-cores
+\emph default
+, where they are transformed according to the soft-cores' algorithms.
+ After running the gauntlet of soft-cores, the samples flow first to a buffering
+ FIFO, and finally to a 
+\emph on
+mixer
+\emph default
+, which sends the samples off to be played by speakers of stored in a file.
+\end_layout
+
+\begin_layout Subsection*
+A more detailed look a our system
+\end_layout
+
+\begin_layout Standard
+Our audio pipeline starts its life with whatever music we want to play already
+ in memory.
+ The music has multiple tracks, or 
+\begin_inset Quotes eld
+\end_inset
+
+voices,
+\begin_inset Quotes erd
+\end_inset
+
+ which we arrange on the memory in contiguous sequences.
+ Therefore, each voice starts at its own start-address, and continues on
+ for as long as it needs.
+ We cap each voice with an end-of-file marker.
+ We make every voice the same length to simplify timing issues, even though
+ that might mean that there is a lot of wasted space in the form of dead
+ areas with no sound.
+\end_layout
+
+\begin_layout Standard
+When the processing starts, the DMA reads in each voice and sends the audio
+ data (
+\begin_inset Quotes eld
+\end_inset
+
+samples
+\begin_inset Quotes erd
+\end_inset
+
+) off to a chain of soft-cores.
+ The DMA knows to which chain the samples should be forwarded by looking
+ up the samples' voice in a hash table read at startup.
+ Once the samples enter the soft-core chain, the first soft-core in line
+ takes the samples and performs some sort of audio operation, producing
+ modified audio samples.
+ These samples feed into the next soft-core which performs a different algorithm.
+ As condition for functional correctness, we require the algorithm that
+ each soft-core contains to be able to produce audio samples at the desired
+ 44khz rate, but we allow an arbitrary setup time for the soft-core to get
+ ready.
+ That way, a pipelined processor can take its time and fill up its pipeline
+ completely with no worries.
+ Once the soft-core starts producing samples, it must produce them at a
+ rate of at least 44khz forever.
+ If every soft-core in the chain obeys this timing condition, then the whole
+ chain will as well, so the entire chain of soft-cores can be treated as
+ a single big soft-core for timing purposes.
+ Our soft-cores are just Lab 5 processors preloaded with specific audio
+ processing algorithms.
+\end_layout
+
+\begin_layout Standard
+Eventually, the samples make their way to the end of the chain of soft-cores.
+ Every chain of soft-cores ends in a FIFO.
+ For this project, we will have 12 separate voices.
+ Therefore, there will be 12 soft-core chains, each with a FIFO at its end,
+ one for each voice.
+ Each of the 12 FIFOs leads to the mixer, which only begins operation once
+ all 12 FIFOs are full.
+ Because of the timing constraints we impose on our soft-cores, once every
+ FIFO has at least one sample, all 12 will forever more be able to supply
+ samples at 44khz.
+ The mixer therefore waits until all 12 FIFOs have elements and then reads
+ samples from all FIFOS at a rate of 44khz.
+ The mixer combines the samples through simple addition and scaling, creating
+ a single stream of sample data, which is sent back from the FPGA to the
+ host computer where we play the stream and/or save it to a file.
+ The mixer ensures that it outputs samples at a rate of 44khz by running
+ everything through its own internal buffer FIFO clocked at 44khz.
+\end_layout
+
+\end_body
+\end_document
diff -r 000000000000 -r 6d1ff93e3afa documents/AudioProcessing.pdf
Binary file documents/AudioProcessing.pdf has changed