With most decoders it is quick, easy and reliable to get a particular
piece of content from a particular timecode. This applies to the DCP,
-DCP subtitle, Sndfile and Image decoders. With FFmpeg, however, this is not easy.
+DCP subtitle, Image and Video MXF decoders. With FFmpeg, however,
+this is not easy.
This suggests that it would make more sense to keep the
decode-and-see-what-comes-out code within the FFmpeg decoder and not
However resampling screws this up, as it means all audio requires
decode-and-see. I don't think you can't resample in neat blocks as
-there are fractional samples other complications. You can't postpone
+there are fractional samples and other complications. You can't postpone
resampling to the end of the player since different audio may be
coming in at different rates.
a bit ridiculous when most of the decoders have slightly clunky seek
and pass methods.
+Having said that: the only other decoder which produces audio is now
+the DCP one, and maybe that never needs to be resampled.
+
\section{Multiple streams}
Player then emits the `final cut', which must have properties like no
gaps in video/audio.
-One problem I remember is which decoder to pass() at any given time:
+Maybe you could have a parent class for simpler get-stuff-at-this-time
+decoders to give them \texttt{pass()} / \texttt{seek()}.
+
+One problem I remember is which decoder to \texttt{pass()} at any given time:
it must be the one with the earliest last output, presumably.
Resampling also looks fiddly in the v1 code.
-Possible steps:
-\begin{enumerate}
-\item Add signals to \texttt{Player}; remove \texttt{get\_*}
-\item Give player a \texttt{pass()} which calls decoders and sanitises
- output.
-\item Make transcoder attach to \texttt{Player} and pass output through to encoding.
-\item Make preview attach to \texttt{Player}, buffer the output and then fetch it from a UI thread.
-\end{enumerate}
+
+\section{Having a go}
+
+\begin{lstlisting}
+ class Decoder {
+ virtual void pass() = 0;
+ virtual void seek(ContentTime time, bool accurate) = 0;
+
+ signals2<void (ContentVideo)> Video;
+ signals2<void (ContentAudio, AudioStreamPtr)> Audio;
+ signals2<void (ContentTextSubtitle)> TextSubtitle;
+ };
+\end{lstlisting}
+
+or perhaps
+
+\begin{lstlisting}
+ class Decoder {
+ virtual void pass() = 0;
+ virtual void seek(ContentTime time, bool accurate) = 0;
+
+ shared_ptr<VideoDecoder> video;
+ shared_ptr<AudioDecoder> audio;
+ shared_ptr<SubtitleDecoder> subtitle;
+ };
+
+ class VideoDecoder {
+ signals2<void (ContentVideo)> Data;
+ };
+\end{lstlisting}
+
+Questions:
+\begin{itemize}
+\item Video / audio frame or \texttt{ContentTime}?
+\end{itemize}
\end{document}