aacsbr: prevent multiple ff_aac_sbr_ctx_init()
[ffmpeg.git] / libavcodec / alac.c
index 2f08f2d..06bf6f8 100644 (file)
  */
 
 /**
- * @file alac.c
+ * @file
  * ALAC (Apple Lossless Audio Codec) decoder
  * @author 2005 David Hammerton
- *
- * For more information on the ALAC format, visit:
- *  http://crazney.net/programs/itunes/alac.html
+ * @see http://crazney.net/programs/itunes/alac.html
  *
  * Note: This decoder expects a 36- (0x24-)byte QuickTime atom to be
  * passed through the extradata[_size] fields. This atom is tacked onto
 
 
 #include "avcodec.h"
-#include "bitstream.h"
+#include "get_bits.h"
 #include "bytestream.h"
+#include "unary.h"
+#include "mathops.h"
 
 #define ALAC_EXTRADATA_SIZE 36
 #define MAX_CHANNELS 2
@@ -63,11 +63,7 @@ typedef struct {
 
     AVCodecContext *avctx;
     GetBitContext gb;
-    /* init to 0; first frame decode should initialize from extradata and
-     * set this to 1 */
-    int context_initialized;
 
-    int samplesize;
     int numchannels;
     int bytespersample;
 
@@ -76,20 +72,17 @@ typedef struct {
 
     int32_t *outputsamples_buffer[MAX_CHANNELS];
 
+    int32_t *wasted_bits_buffer[MAX_CHANNELS];
+
     /* stuff from setinfo */
     uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
-    uint8_t setinfo_7a; /* 0x00 */
     uint8_t setinfo_sample_size; /* 0x10 */
     uint8_t setinfo_rice_historymult; /* 0x28 */
     uint8_t setinfo_rice_initialhistory; /* 0x0a */
     uint8_t setinfo_rice_kmodifier; /* 0x0e */
-    uint8_t setinfo_7f; /* 0x02 */
-    uint16_t setinfo_80; /* 0x00ff */
-    uint32_t setinfo_82; /* 0x000020e7 */ /* max sample size?? */
-    uint32_t setinfo_86; /* 0x00069fe4 */ /* bit rate (average)?? */
-    uint32_t setinfo_8a_rate; /* 0x0000ac44 */
     /* end setinfo stuff */
 
+    int wasted_bits;
 } ALACContext;
 
 static void allocate_buffers(ALACContext *alac)
@@ -101,12 +94,14 @@ static void allocate_buffers(ALACContext *alac)
 
         alac->outputsamples_buffer[chan] =
             av_malloc(alac->setinfo_max_samples_per_frame * 4);
+
+        alac->wasted_bits_buffer[chan] = av_malloc(alac->setinfo_max_samples_per_frame * 4);
     }
 }
 
 static int alac_set_info(ALACContext *alac)
 {
-    unsigned char *ptr = alac->avctx->extradata;
+    const unsigned char *ptr = alac->avctx->extradata;
 
     ptr += 4; /* size */
     ptr += 4; /* alac */
@@ -119,29 +114,51 @@ static int alac_set_info(ALACContext *alac)
 
     /* buffer size / 2 ? */
     alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
-    alac->setinfo_7a                    = *ptr++;
+    ptr++;                          /* ??? */
     alac->setinfo_sample_size           = *ptr++;
+    if (alac->setinfo_sample_size > 32) {
+        av_log(alac->avctx, AV_LOG_ERROR, "setinfo_sample_size too large\n");
+        return -1;
+    }
     alac->setinfo_rice_historymult      = *ptr++;
     alac->setinfo_rice_initialhistory   = *ptr++;
     alac->setinfo_rice_kmodifier        = *ptr++;
-    /* channels? */
-    alac->setinfo_7f                    = *ptr++;
-    alac->setinfo_80                    = bytestream_get_be16(&ptr);
-    /* max coded frame size */
-    alac->setinfo_82                    = bytestream_get_be32(&ptr);
-    /* bitrate ? */
-    alac->setinfo_86                    = bytestream_get_be32(&ptr);
-    /* samplerate */
-    alac->setinfo_8a_rate               = bytestream_get_be32(&ptr);
+    ptr++;                         /* channels? */
+    bytestream_get_be16(&ptr);      /* ??? */
+    bytestream_get_be32(&ptr);      /* max coded frame size */
+    bytestream_get_be32(&ptr);      /* bitrate ? */
+    bytestream_get_be32(&ptr);      /* samplerate */
 
     allocate_buffers(alac);
 
     return 0;
 }
 
-static inline int count_leading_zeros(int32_t input)
-{
-    return 31-av_log2(input);
+static inline int decode_scalar(GetBitContext *gb, int k, int limit, int readsamplesize){
+    /* read x - number of 1s before 0 represent the rice */
+    int x = get_unary_0_9(gb);
+
+    if (x > 8) { /* RICE THRESHOLD */
+        /* use alternative encoding */
+        x = get_bits(gb, readsamplesize);
+    } else {
+        if (k >= limit)
+            k = limit;
+
+        if (k != 1) {
+            int extrabits = show_bits(gb, k);
+
+            /* multiply x by 2^k - 1, as part of their strange algorithm */
+            x = (x << k) - x;
+
+            if (extrabits > 1) {
+                x += extrabits - 1;
+                skip_bits(gb, k);
+            } else
+                skip_bits(gb, k - 1);
+        }
+    }
+    return x;
 }
 
 static void bastardized_rice_decompress(ALACContext *alac,
@@ -159,53 +176,16 @@ static void bastardized_rice_decompress(ALACContext *alac,
     int sign_modifier = 0;
 
     for (output_count = 0; output_count < output_size; output_count++) {
-        int32_t x = 0;
+        int32_t x;
         int32_t x_modified;
         int32_t final_val;
 
-        /* read x - number of 1s before 0 represent the rice */
-        while (x <= 8 && get_bits1(&alac->gb)) {
-            x++;
-        }
-
+        /* standard rice encoding */
+        int k; /* size of extra bits */
 
-        if (x > 8) { /* RICE THRESHOLD */
-            /* use alternative encoding */
-            int32_t value;
-
-            value = get_bits(&alac->gb, readsamplesize);
-
-            /* mask value to readsamplesize size */
-            if (readsamplesize != 32)
-                value &= (0xffffffff >> (32 - readsamplesize));
-
-            x = value;
-        } else {
-            /* standard rice encoding */
-            int extrabits;
-            int k; /* size of extra bits */
-
-            /* read k, that is bits as is */
-            k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3);
-
-            if (k < 0)
-                k += rice_kmodifier;
-            else
-                k = rice_kmodifier;
-
-            if (k != 1) {
-                extrabits = show_bits(&alac->gb, k);
-
-                /* multiply x by 2^k - 1, as part of their strange algorithm */
-                x = (x << k) - x;
-
-                if (extrabits > 1) {
-                    x += extrabits - 1;
-                    get_bits(&alac->gb, k);
-                } else
-                    get_bits(&alac->gb, k - 1);
-            }
-        }
+        /* read k, that is bits as is */
+        k = av_log2((history >> 9) + 3);
+        x= decode_scalar(&alac->gb, k, rice_kmodifier, readsamplesize);
 
         x_modified = sign_modifier + x;
         final_val = (x_modified + 1) / 2;
@@ -224,39 +204,20 @@ static void bastardized_rice_decompress(ALACContext *alac,
 
         /* special case: there may be compressed blocks of 0 */
         if ((history < 128) && (output_count+1 < output_size)) {
-            int block_size;
+            int k;
+            unsigned int block_size;
 
             sign_modifier = 1;
 
-            x = 0;
-            while (x <= 8 && get_bits1(&alac->gb)) {
-                x++;
-            }
-
-            if (x > 8) {
-                block_size = get_bits(&alac->gb, 16);
-                block_size &= 0xffff;
-            } else {
-                int k;
-                int extrabits;
-
-                k = count_leading_zeros(history) + ((history + 16) >> 6 /* / 64 */) - 24;
+            k = 7 - av_log2(history) + ((history + 16) >> 6 /* / 64 */);
 
-                extrabits = show_bits(&alac->gb, k);
-
-                block_size = (((1 << k) - 1) & rice_kmodifier_mask) * x
-                           + extrabits - 1;
-
-                if (extrabits < 2) {
-                    x = 1 - extrabits;
-                    block_size += x;
-                    get_bits(&alac->gb, k - 1);
-                } else {
-                    get_bits(&alac->gb, k);
-                }
-            }
+            block_size= decode_scalar(&alac->gb, k, rice_kmodifier, 16);
 
             if (block_size > 0) {
+                if(block_size >= output_size - output_count){
+                    av_log(alac->avctx, AV_LOG_ERROR, "invalid zero block size of %d %d %d\n", block_size, output_size, output_count);
+                    block_size= output_size - output_count - 1;
+                }
                 memset(&output_buffer[output_count+1], 0, block_size * 4);
                 output_count += block_size;
             }
@@ -269,12 +230,10 @@ static void bastardized_rice_decompress(ALACContext *alac,
     }
 }
 
-#define SIGN_EXTENDED32(val, bits) ((val << (32 - bits)) >> (32 - bits))
-
-#define SIGN_ONLY(v) \
-                     ((v < 0) ? (-1) : \
-                                ((v > 0) ? (1) : \
-                                           (0)))
+static inline int sign_only(int v)
+{
+    return v ? FFSIGN(v) : 0;
+}
 
 static void predictor_decompress_fir_adapt(int32_t *error_buffer,
                                            int32_t *buffer_out,
@@ -310,7 +269,7 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
             prev_value = buffer_out[i];
             error_value = error_buffer[i+1];
             buffer_out[i+1] =
-                SIGN_EXTENDED32((prev_value + error_value), readsamplesize);
+                sign_extend((prev_value + error_value), readsamplesize);
         }
         return;
     }
@@ -321,24 +280,13 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
             int32_t val;
 
             val = buffer_out[i] + error_buffer[i+1];
-            val = SIGN_EXTENDED32(val, readsamplesize);
+            val = sign_extend(val, readsamplesize);
             buffer_out[i+1] = val;
         }
 
-#if 0
     /* 4 and 8 are very common cases (the only ones i've seen). these
-     * should be unrolled and optimised
+     * should be unrolled and optimized
      */
-    if (predictor_coef_num == 4) {
-        /* FIXME: optimised general case */
-        return;
-    }
-
-    if (predictor_coef_table == 8) {
-        /* FIXME: optimised general case */
-        return;
-    }
-#endif
 
     /* general case */
     if (predictor_coef_num > 0) {
@@ -356,7 +304,7 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
             outval = (1 << (predictor_quantitization-1)) + sum;
             outval = outval >> predictor_quantitization;
             outval = outval + buffer_out[0] + error_val;
-            outval = SIGN_EXTENDED32(outval, readsamplesize);
+            outval = sign_extend(outval, readsamplesize);
 
             buffer_out[predictor_coef_num+1] = outval;
 
@@ -365,7 +313,7 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
 
                 while (predictor_num >= 0 && error_val > 0) {
                     int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
-                    int sign = SIGN_ONLY(val);
+                    int sign = sign_only(val);
 
                     predictor_coef_table[predictor_num] -= sign;
 
@@ -381,7 +329,7 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
 
                 while (predictor_num >= 0 && error_val < 0) {
                     int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
-                    int sign = - SIGN_ONLY(val);
+                    int sign = - sign_only(val);
 
                     predictor_coef_table[predictor_num] -= sign;
 
@@ -439,38 +387,75 @@ static void reconstruct_stereo_16(int32_t *buffer[MAX_CHANNELS],
     }
 }
 
+static void decorrelate_stereo_24(int32_t *buffer[MAX_CHANNELS],
+                                  int32_t *buffer_out,
+                                  int32_t *wasted_bits_buffer[MAX_CHANNELS],
+                                  int wasted_bits,
+                                  int numchannels, int numsamples,
+                                  uint8_t interlacing_shift,
+                                  uint8_t interlacing_leftweight)
+{
+    int i;
+
+    if (numsamples <= 0)
+        return;
+
+    /* weighted interlacing */
+    if (interlacing_leftweight) {
+        for (i = 0; i < numsamples; i++) {
+            int32_t a, b;
+
+            a = buffer[0][i];
+            b = buffer[1][i];
+
+            a -= (b * interlacing_leftweight) >> interlacing_shift;
+            b += a;
+
+            if (wasted_bits) {
+                b  = (b  << wasted_bits) | wasted_bits_buffer[0][i];
+                a  = (a  << wasted_bits) | wasted_bits_buffer[1][i];
+            }
+
+            buffer_out[i * numchannels]     = b << 8;
+            buffer_out[i * numchannels + 1] = a << 8;
+        }
+    } else {
+        for (i = 0; i < numsamples; i++) {
+            int32_t left, right;
+
+            left  = buffer[0][i];
+            right = buffer[1][i];
+
+            if (wasted_bits) {
+                left   = (left   << wasted_bits) | wasted_bits_buffer[0][i];
+                right  = (right  << wasted_bits) | wasted_bits_buffer[1][i];
+            }
+
+            buffer_out[i * numchannels]     = left  << 8;
+            buffer_out[i * numchannels + 1] = right << 8;
+        }
+    }
+}
+
 static int alac_decode_frame(AVCodecContext *avctx,
                              void *outbuffer, int *outputsize,
-                             uint8_t *inbuffer, int input_buffer_size)
+                             AVPacket *avpkt)
 {
+    const uint8_t *inbuffer = avpkt->data;
+    int input_buffer_size = avpkt->size;
     ALACContext *alac = avctx->priv_data;
 
     int channels;
-    int32_t outputsamples;
+    unsigned int outputsamples;
     int hassize;
-    int readsamplesize;
-    int wasted_bytes;
+    unsigned int readsamplesize;
     int isnotcompressed;
     uint8_t interlacing_shift;
     uint8_t interlacing_leftweight;
 
     /* short-circuit null buffers */
     if (!inbuffer || !input_buffer_size)
-        return input_buffer_size;
-
-    /* initialize from the extradata */
-    if (!alac->context_initialized) {
-        if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
-            av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
-                ALAC_EXTRADATA_SIZE);
-            return input_buffer_size;
-        }
-        if (alac_set_info(alac)) {
-            av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
-            return input_buffer_size;
-        }
-        alac->context_initialized = 1;
-    }
+        return -1;
 
     init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
 
@@ -478,40 +463,65 @@ static int alac_decode_frame(AVCodecContext *avctx,
     if (channels > MAX_CHANNELS) {
         av_log(avctx, AV_LOG_ERROR, "channels > %d not supported\n",
                MAX_CHANNELS);
-        return input_buffer_size;
+        return -1;
     }
 
     /* 2^result = something to do with output waiting.
      * perhaps matters if we read > 1 frame in a pass?
      */
-    get_bits(&alac->gb, 4);
+    skip_bits(&alac->gb, 4);
 
-    get_bits(&alac->gb, 12); /* unknown, skip 12 bits */
+    skip_bits(&alac->gb, 12); /* unknown, skip 12 bits */
 
     /* the output sample size is stored soon */
     hassize = get_bits1(&alac->gb);
 
-    wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */
+    alac->wasted_bits = get_bits(&alac->gb, 2) << 3;
 
     /* whether the frame is compressed */
     isnotcompressed = get_bits1(&alac->gb);
 
     if (hassize) {
         /* now read the number of samples as a 32bit integer */
-        outputsamples = get_bits(&alac->gb, 32);
+        outputsamples = get_bits_long(&alac->gb, 32);
+        if(outputsamples > alac->setinfo_max_samples_per_frame){
+            av_log(avctx, AV_LOG_ERROR, "outputsamples %d > %d\n", outputsamples, alac->setinfo_max_samples_per_frame);
+            return -1;
+        }
     } else
         outputsamples = alac->setinfo_max_samples_per_frame;
 
+    switch (alac->setinfo_sample_size) {
+    case 16: avctx->sample_fmt    = AV_SAMPLE_FMT_S16;
+             alac->bytespersample = channels << 1;
+             break;
+    case 24: avctx->sample_fmt    = AV_SAMPLE_FMT_S32;
+             alac->bytespersample = channels << 2;
+             break;
+    default: av_log(avctx, AV_LOG_ERROR, "Sample depth %d is not supported.\n",
+                    alac->setinfo_sample_size);
+             return -1;
+    }
+
+    if(outputsamples > *outputsize / alac->bytespersample){
+        av_log(avctx, AV_LOG_ERROR, "sample buffer too small\n");
+        return -1;
+    }
+
     *outputsize = outputsamples * alac->bytespersample;
-    readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + channels - 1;
+    readsamplesize = alac->setinfo_sample_size - (alac->wasted_bits) + channels - 1;
+    if (readsamplesize > MIN_CACHE_BITS) {
+        av_log(avctx, AV_LOG_ERROR, "readsamplesize too big (%d)\n", readsamplesize);
+        return -1;
+    }
 
     if (!isnotcompressed) {
         /* so it is compressed */
-        int16_t predictor_coef_table[channels][32];
-        int predictor_coef_num[channels];
-        int prediction_type[channels];
-        int prediction_quantitization[channels];
-        int ricemodifier[channels];
+        int16_t predictor_coef_table[MAX_CHANNELS][32];
+        int predictor_coef_num[MAX_CHANNELS];
+        int prediction_type[MAX_CHANNELS];
+        int prediction_quantitization[MAX_CHANNELS];
+        int ricemodifier[MAX_CHANNELS];
         int i, chan;
 
         interlacing_shift = get_bits(&alac->gb, 8);
@@ -529,9 +539,13 @@ static int alac_decode_frame(AVCodecContext *avctx,
                 predictor_coef_table[chan][i] = (int16_t)get_bits(&alac->gb, 16);
         }
 
-        if (wasted_bytes)
-            av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
-
+        if (alac->wasted_bits) {
+            int i, ch;
+            for (i = 0; i < outputsamples; i++) {
+                for (ch = 0; ch < channels; ch++)
+                    alac->wasted_bits_buffer[ch][i] = get_bits(&alac->gb, alac->wasted_bits);
+            }
+        }
         for (chan = 0; chan < channels; chan++) {
             bastardized_rice_decompress(alac,
                                         alac->predicterror_buffer[chan],
@@ -563,37 +577,32 @@ static int alac_decode_frame(AVCodecContext *avctx,
         }
     } else {
         /* not compressed, easy case */
+        int i, chan;
         if (alac->setinfo_sample_size <= 16) {
-            int i, chan;
-            for (chan = 0; chan < channels; chan++)
-                for (i = 0; i < outputsamples; i++) {
-                    int32_t audiobits;
+        for (i = 0; i < outputsamples; i++)
+            for (chan = 0; chan < channels; chan++) {
+                int32_t audiobits;
 
-                    audiobits = get_bits(&alac->gb, alac->setinfo_sample_size);
-                    audiobits = SIGN_EXTENDED32(audiobits, readsamplesize);
+                audiobits = get_sbits_long(&alac->gb, alac->setinfo_sample_size);
 
-                    alac->outputsamples_buffer[chan][i] = audiobits;
-                }
+                alac->outputsamples_buffer[chan][i] = audiobits;
+            }
         } else {
-            int i, chan;
-            for (chan = 0; chan < channels; chan++)
-                for (i = 0; i < outputsamples; i++) {
-                    int32_t audiobits;
-
-                    audiobits = get_bits(&alac->gb, 16);
-                    /* special case of sign extension..
-                     * as we'll be ORing the low 16bits into this */
-                    audiobits = audiobits << 16;
-                    audiobits = audiobits >> (32 - alac->setinfo_sample_size);
-                    audiobits |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);
-
-                    alac->outputsamples_buffer[chan][i] = audiobits;
+            for (i = 0; i < outputsamples; i++) {
+                for (chan = 0; chan < channels; chan++) {
+                    alac->outputsamples_buffer[chan][i] = get_bits(&alac->gb,
+                                                          alac->setinfo_sample_size);
+                    alac->outputsamples_buffer[chan][i] = sign_extend(alac->outputsamples_buffer[chan][i],
+                                                                      alac->setinfo_sample_size);
                 }
+            }
         }
-        /* wasted_bytes = 0; */
+        alac->wasted_bits = 0;
         interlacing_shift = 0;
         interlacing_leftweight = 0;
     }
+    if (get_bits(&alac->gb, 3) != 7)
+        av_log(avctx, AV_LOG_ERROR, "Error : Wrong End Of Frame\n");
 
     switch(alac->setinfo_sample_size) {
     case 16:
@@ -607,56 +616,75 @@ static int alac_decode_frame(AVCodecContext *avctx,
         } else {
             int i;
             for (i = 0; i < outputsamples; i++) {
-                int16_t sample = alac->outputsamples_buffer[0][i];
-                ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
+                ((int16_t*)outbuffer)[i] = alac->outputsamples_buffer[0][i];
             }
         }
         break;
-    case 20:
     case 24:
-    case 32:
-        av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
-        break;
-    default:
+        if (channels == 2) {
+            decorrelate_stereo_24(alac->outputsamples_buffer,
+                                  outbuffer,
+                                  alac->wasted_bits_buffer,
+                                  alac->wasted_bits,
+                                  alac->numchannels,
+                                  outputsamples,
+                                  interlacing_shift,
+                                  interlacing_leftweight);
+        } else {
+            int i;
+            for (i = 0; i < outputsamples; i++)
+                ((int32_t *)outbuffer)[i] = alac->outputsamples_buffer[0][i] << 8;
+        }
         break;
     }
 
+    if (input_buffer_size * 8 - get_bits_count(&alac->gb) > 8)
+        av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n", input_buffer_size * 8 - get_bits_count(&alac->gb));
+
     return input_buffer_size;
 }
 
-static int alac_decode_init(AVCodecContext * avctx)
+static av_cold int alac_decode_init(AVCodecContext * avctx)
 {
     ALACContext *alac = avctx->priv_data;
     alac->avctx = avctx;
-    alac->context_initialized = 0;
-
-    alac->samplesize = alac->avctx->bits_per_sample;
     alac->numchannels = alac->avctx->channels;
-    alac->bytespersample = (alac->samplesize / 8) * alac->numchannels;
+
+    /* initialize from the extradata */
+    if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
+        av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
+            ALAC_EXTRADATA_SIZE);
+        return -1;
+    }
+    if (alac_set_info(alac)) {
+        av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
+        return -1;
+    }
 
     return 0;
 }
 
-static int alac_decode_close(AVCodecContext *avctx)
+static av_cold int alac_decode_close(AVCodecContext *avctx)
 {
     ALACContext *alac = avctx->priv_data;
 
     int chan;
     for (chan = 0; chan < MAX_CHANNELS; chan++) {
-        av_free(alac->predicterror_buffer[chan]);
-        av_free(alac->outputsamples_buffer[chan]);
+        av_freep(&alac->predicterror_buffer[chan]);
+        av_freep(&alac->outputsamples_buffer[chan]);
+        av_freep(&alac->wasted_bits_buffer[chan]);
     }
 
     return 0;
 }
 
-AVCodec alac_decoder = {
-    "alac",
-    CODEC_TYPE_AUDIO,
-    CODEC_ID_ALAC,
-    sizeof(ALACContext),
-    alac_decode_init,
-    NULL,
-    alac_decode_close,
-    alac_decode_frame,
+AVCodec ff_alac_decoder = {
+    .name           = "alac",
+    .type           = AVMEDIA_TYPE_AUDIO,
+    .id             = CODEC_ID_ALAC,
+    .priv_data_size = sizeof(ALACContext),
+    .init           = alac_decode_init,
+    .close          = alac_decode_close,
+    .decode         = alac_decode_frame,
+    .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
 };