FLAC: Conditionally increase MAX_BLOCKSIZE to 8KB

High-frequency files increasingly use a block size of over 4608B, which
means we need larger buffers to decode them.  However, larger buffers no
longer fit in IRAM on less-capable devices, hurting performance for
"normal" file playback.

On our slowest devices (M68K and PP-based devices), this is not worth
the tradeoff as they will likely not have enough CPU oomph to decode and
downmix these files in realtime.

S5L87xx-based devices have the raw performance to do this, so we decided
to err on the side of wider file compatibility at the cost of some
performance.

All other devices are unaffected.

Change-Id: I7344cf4c8c6b7b5c14f1ea67381160665d6ece5b

lib/rbcodec/codecs/libffmpegFLAC/README.rockbox

@@ -25,8 +25,10 @@ In order to minimise memory usage, a small number of hard-coded limits
 are present in decoder.h - mainly limiting the supported blocksize
 (number of samples in a frame) to 4608.  This is the default value
 used by the reference FLAC encoder at all standard compression
-settings.
+settings.  However, it is increasingly common for high-resolution/freq
-
+files to use 8K block sizes, so on devices that can play back such
+files natively and/or have sufficient processor oomph to downmix in
+realtime, we use that larger limit.
 
 TESTING
 

lib/rbcodec/codecs/libffmpegFLAC/bitstream.h

@@ -19,22 +19,13 @@
 #endif
 
 #if (CONFIG_CPU == MCF5250) || (CONFIG_CPU == PP5022) || \
-    (CONFIG_CPU == PP5024) || (CONFIG_CPU == S5L8702)
+    (CONFIG_CPU == PP5024)
 #define ICODE_ATTR_FLAC ICODE_ATTR
 #define IBSS_ATTR_FLAC  IBSS_ATTR
 /* Enough IRAM to move additional data to it. */
 #define IBSS_ATTR_FLAC_LARGE_IRAM   IBSS_ATTR
 #define IBSS_ATTR_FLAC_XLARGE_IRAM
 #define IBSS_ATTR_FLAC_XXLARGE_IRAM
-
-#elif (CONFIG_CPU == S5L8700) || (CONFIG_CPU == S5L8701)
-#define ICODE_ATTR_FLAC ICODE_ATTR
-#define IBSS_ATTR_FLAC  IBSS_ATTR
-/* Enough IRAM to move even more additional data to it. */
-#define IBSS_ATTR_FLAC_LARGE_IRAM   IBSS_ATTR
-#define IBSS_ATTR_FLAC_XLARGE_IRAM  IBSS_ATTR
-#define IBSS_ATTR_FLAC_XXLARGE_IRAM
-
 #else
 #define ICODE_ATTR_FLAC ICODE_ATTR
 #define IBSS_ATTR_FLAC  IBSS_ATTR
@@ -44,6 +35,12 @@
 #define IBSS_ATTR_FLAC_XXLARGE_IRAM
 #endif
 
+#if (ARCH == ARCH_M68K) || defined(CPU_PP) || MEMORYSIZE <= 2
+#define MAX_BLOCKSIZE 4608
+#else
+#define MAX_BLOCKSIZE 8192
+#endif
+
 /* Endian conversion routines for standalone compilation */
 #ifdef BUILD_STANDALONE
     #ifdef BUILD_BIGENDIAN

lib/rbcodec/codecs/libffmpegFLAC/decoder.h

@@ -4,7 +4,9 @@
 #include "bitstream.h"
 
 #define MAX_CHANNELS   7      /* Maximum supported channels, only left/right will be played back */
+#ifndef MAX_BLOCKSIZE
 #define MAX_BLOCKSIZE  4608   /* Maxsize in samples of one uncompressed frame */
+#endif
 #define MAX_FRAMESIZE  65536  /* Maxsize in bytes of one compressed frame */
 #define MIN_FRAME_SIZE 11     /* smallest valid FLAC frame possible */
 

manual/appendix/file_formats.tex

@@ -146,7 +146,10 @@
         & Linear PCM 8/16/24/32 bit, IEEE float 32/64 bit, ITU-T G.711 a-law/$\mu$-law\\
     Free Lossless Audio
         & \fname{.flac}
-        & Supports multichannel playback including downmixing to stereo.\\
+        & Multichannel and/or high-resolution files will be downmixed to 16-bit stereo. 
+	\opt{ipod,iriverh10,sansaclip,sansam200v4,sansac200v2,iriverh100,iriverh300,iaudiox5,iaudiom5,iaudiom3,mpiohd200,mpiphd300}{
+	    \nopt{ipodnano2g,ipod6g}{Due to resource constraints, files with large block sizes are not supported, and realtime playback may not be possible where downmixing is necessary.}}
+	\\
     Apple Lossless
         & \fname{.m4a}, \fname{.mp4}
         & \\