Add design doc.

[dcpomatic.git] / doc / design / resampling.tex

diff --git a/doc/design/resampling.tex b/doc/design/resampling.tex
index c1a1d346322f9cfde11e371322cb18e4687a91c6..22d88e3759aca46d27f82b34ace79676659f82dd 100644 (file)
--- a/doc/design/resampling.tex
+++ b/doc/design/resampling.tex
@@ -85,4 +85,17 @@ so this is equivalent to marking the original, unsampled audio as $C_A S$.
 Then we set $Q = 48$kHz so that $P = 48000 / S$, or $P = C_V F_A
 / F_V$.
 
+Note that the original sampling rate of the audio content is
+irrelevant.  Also, skipping or doubling of video frames is analagous
+to audio resampling: the data are the same, just represented with more
+or fewer samples.
+
+
+\section{Further thoughts}
+
+Consider the case where the content video rate $C_V = 24$ and the DCP
+video rate $F_V = 25$.  Then 46080 (resampled) samples of audio
+content last 1s at the original rate or $24/25$s at the DCP rate and
+1s of DCP is made up of 48000 (resampled) content samples.
+
 \end{document}