apedec: allow the user to set the maximum number of output samples per call

It makes sense in some cases to split up the output packet to save on memory
usage (ape frames can be very large), but the current/default size is
arbitrary. Allowing the user to configure this gives more flexibility and
requires minimal additional code.

libavcodec/apedec.c

@@ -25,13 +25,13 @@
 #include "bytestream.h"
 #include "libavutil/audioconvert.h"
 #include "libavutil/avassert.h"
+#include "libavutil/opt.h"
 
 /**
  * @file
  * Monkey's Audio lossless audio decoder
  */
 
-#define BLOCKS_PER_LOOP     4608
 #define MAX_CHANNELS        2
 #define MAX_BYTESPERSAMPLE  3
 
@@ -126,6 +126,7 @@ typedef struct APEPredictor {
 
 /** Decoder context */
 typedef struct APEContext {
+    AVClass *class;                          ///< class for AVOptions
     AVCodecContext *avctx;
     AVFrame frame;
     DSPContext dsp;
@@ -145,6 +146,7 @@ typedef struct APEContext {
     int32_t *decoded_buffer;
     int decoded_size;
     int32_t *decoded[MAX_CHANNELS];          ///< decoded data for each channel
+    int blocks_per_loop;                     ///< maximum number of samples to decode for each call
 
     int16_t* filterbuf[APE_FILTER_LEVELS];   ///< filter memory
 
@@ -891,7 +893,7 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
         return avpkt->size;
     }
 
-    blockstodecode = FFMIN(BLOCKS_PER_LOOP, s->samples);
+    blockstodecode = FFMIN(s->blocks_per_loop, s->samples);
 
     /* reallocate decoded sample buffer if needed */
     av_fast_malloc(&s->decoded_buffer, &s->decoded_size,
@@ -964,6 +966,21 @@ static void ape_flush(AVCodecContext *avctx)
     s->samples= 0;
 }
 
+#define OFFSET(x) offsetof(APEContext, x)
+#define PAR (AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_AUDIO_PARAM)
+static const AVOption options[] = {
+    { "max_samples", "maximum number of samples decoded per call",             OFFSET(blocks_per_loop), AV_OPT_TYPE_INT,   { 4608 },    1,       INT_MAX, PAR, "max_samples" },
+    { "all",         "no maximum. decode all samples for each packet at once", 0,                       AV_OPT_TYPE_CONST, { INT_MAX }, INT_MIN, INT_MAX, PAR, "max_samples" },
+    { NULL},
+};
+
+static const AVClass ape_decoder_class = {
+    .class_name = "APE decoder",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 AVCodec ff_ape_decoder = {
     .name           = "ape",
     .type           = AVMEDIA_TYPE_AUDIO,
@@ -975,4 +992,5 @@ AVCodec ff_ape_decoder = {
     .capabilities   = CODEC_CAP_SUBFRAMES | CODEC_CAP_DELAY | CODEC_CAP_DR1,
     .flush = ape_flush,
     .long_name = NULL_IF_CONFIG_SMALL("Monkey's Audio"),
+    .priv_class     = &ape_decoder_class,
 };