libavcodec/flacdec: Implement decoding of 32 bit-per-sample PCM

Add decoding of FLAC files coding for 32 bit-per-sample PCM to libavcodec.

libavcodec/flac.c

@@ -28,7 +28,7 @@
 #include "flacdata.h"
 #include "flac_parse.h"
 
-static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 0 };
+static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 32 };
 
 static const AVChannelLayout flac_channel_layouts[8] = {
     AV_CHANNEL_LAYOUT_MONO,
@@ -82,7 +82,7 @@ int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb,
 
     /* bits per sample */
     bps_code = get_bits(gb, 3);
-    if (bps_code == 3 || bps_code == 7) {
+    if (bps_code == 3) {
         av_log(avctx, AV_LOG_ERROR + log_level_offset,
                "invalid sample size code (%d)\n",
                bps_code);

libavcodec/get_bits.h

@@ -596,6 +596,18 @@ static inline int get_sbits_long(GetBitContext *s, int n)
     return sign_extend(get_bits_long(s, n), n);
 }
 
+/**
+ * Read 0-64 bits as a signed integer.
+ */
+static inline int64_t get_sbits64(GetBitContext *s, int n)
+{
+    // sign_extend(x, 0) is undefined
+    if (!n)
+        return 0;
+
+    return sign_extend64(get_bits64(s, n), n);
+}
+
 /**
  * Show 0-32 bits.
  */

libavcodec/mathops.h

@@ -138,6 +138,15 @@ static inline av_const int sign_extend(int val, unsigned bits)
 }
 #endif
 
+#ifndef sign_extend64
+static inline av_const int64_t sign_extend64(int64_t val, unsigned bits)
+{
+    unsigned shift = 8 * sizeof(int64_t) - bits;
+    union { uint64_t u; int64_t s; } v = { (uint64_t) val << shift };
+    return v.s >> shift;
+}
+#endif
+
 #ifndef zero_extend
 static inline av_const unsigned zero_extend(unsigned val, unsigned bits)
 {