support mp3 decoding over libavcodec

[picodrive.git] / platform / common / mp3_libavcodec.c

diff --git a/platform/common/mp3_libavcodec.c b/platform/common/mp3_libavcodec.c
new file mode 100644 (file)
index 0000000..833b30b
--- /dev/null
+++ b/platform/common/mp3_libavcodec.c
@@ -0,0 +1,117 @@
+/*
+ * Some mp3 related code for Sega/Mega CD.
+ * Uses Libav/FFmpeg libavcodec
+ * (C) notaz, 2013
+ *
+ * This work is licensed under the terms of MAME license.
+ * See COPYING file in the top-level directory.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <libavcodec/avcodec.h>
+
+#include <pico/pico_int.h>
+#include "../libpicofe/lprintf.h"
+#include "mp3.h"
+
+static AVCodecContext *ctx;
+
+int mp3dec_decode(FILE *f, int *file_pos, int file_len)
+{
+       unsigned char input_buf[2 * 1024];
+       int frame_size;
+       AVPacket avpkt;
+       int bytes_in;
+       int bytes_out;
+       int offset;
+       int len;
+
+       av_init_packet(&avpkt);
+
+       do
+       {
+               if (*file_pos >= file_len)
+                       return 1; // EOF, nothing to do
+
+               fseek(f, *file_pos, SEEK_SET);
+               bytes_in = fread(input_buf, 1, sizeof(input_buf), f);
+
+               offset = mp3_find_sync_word(input_buf, bytes_in);
+               if (offset < 0) {
+                       lprintf("find_sync_word (%i/%i) err %i\n",
+                               *file_pos, file_len, offset);
+                       *file_pos = file_len;
+                       return 1; // EOF
+               }
+
+               // to avoid being flooded with "incorrect frame size" errors,
+               // we must calculate and pass exact frame size - lame
+               frame_size = mpeg1_l3_bitrates[input_buf[offset + 2] >> 4];
+               frame_size = frame_size * 144000 / 44100;
+               frame_size += (input_buf[offset + 2] >> 1) & 1;
+
+               if (offset > 0 && bytes_in - offset < frame_size) {
+                       // underflow
+                       *file_pos += offset;
+                       continue;
+               }
+
+               avpkt.data = input_buf + offset;
+               avpkt.size = frame_size;
+               bytes_out = sizeof(cdda_out_buffer);
+
+               len = avcodec_decode_audio3(ctx, cdda_out_buffer,
+                       &bytes_out, &avpkt);
+               if (len <= 0) {
+                       lprintf("mp3 decode err (%i/%i) %i\n",
+                               *file_pos, file_len, len);
+
+                       // attempt to skip the offending frame..
+                       *file_pos += offset + 1;
+                       continue;
+               }
+
+               *file_pos += offset + len;
+       }
+       while (0);
+
+       return 0;
+}
+
+int mp3dec_start(void)
+{
+       AVCodec *codec;
+       int ret;
+
+       if (ctx != NULL)
+               return 0;
+
+       // init decoder
+
+       //avcodec_init();
+       avcodec_register_all();
+
+       // AV_CODEC_ID_MP3 ?
+       codec = avcodec_find_decoder(CODEC_ID_MP3);
+       if (codec == NULL) {
+               lprintf("mp3dec: codec missing\n");
+               return -1;
+       }
+
+       ctx = avcodec_alloc_context();
+       if (ctx == NULL) {
+               lprintf("mp3dec: avcodec_alloc_context failed\n");
+               return -1;
+       }
+
+       ret = avcodec_open(ctx, codec);
+       if (ret < 0) {
+               lprintf("mp3dec: avcodec_open failed: %d\n", ret);
+               av_free(ctx);
+               ctx = NULL;
+               return -1;
+       }
+
+       return 0;
+}