Still more attempts to better find the right mp3 frame header
This commit is contained in:
Ron Pedde
parent
3def3f6e9e
commit
fd70a618d6
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@ -59,6 +59,25 @@
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* Typedefs
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*/
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typedef struct tag_scan_frameinfo {
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int layer;
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int bitrate;
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int samplerate;
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int stereo;
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int frame_length;
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int crc_protected;
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int samples_per_frame;
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int padding;
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int xing_offset;
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double version;
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int is_cbr;
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int is_valid;
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} SCAN_FRAMEINFO;
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typedef struct tag_scan_id3header {
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unsigned char id[3];
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unsigned char version[2];
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@ -1136,6 +1155,135 @@ int scan_get_aacfileinfo(char *file, MP3FILE *pmp3) {
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}
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/**
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* Decode an mp3 frame header. Determine layer, bitrate,
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* samplerate, etc, and fill in the passed structure.
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*
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* @param frame 4 byte mp3 frame header
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* @param pfi pointer to an allocated SCAN_FRAMEINFO struct
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* @return 0 on success (valid frame), -1 otherwise
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*/
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int scan_decode_mp3_frame(unsigned char *frame, SCAN_FRAMEINFO *pfi) {
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int ver;
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int layer_index;
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int sample_index;
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int bitrate_index;
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int samplerate_index;
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if((frame[0] != 0xFF) || (frame[1] < 224)) {
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pfi->is_valid=0;
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return -1;
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}
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ver=(frame[1] & 0x18) >> 3;
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pfi->layer = 4 - ((frame[1] & 0x6) >> 1);
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layer_index=-1;
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sample_index=-1;
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switch(ver) {
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case 0:
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pfi->version = 2.5;
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sample_index=2;
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if(pfi->layer == 1)
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layer_index = 3;
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if((pfi->layer == 2) || (pfi->layer == 3))
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layer_index = 4;
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break;
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case 2:
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pfi->version = 2.0;
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sample_index=1;
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if(pfi->layer == 1)
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layer_index=3;
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if((pfi->layer == 2) || (pfi->layer == 3))
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layer_index=4;
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break;
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case 3:
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pfi->version = 1.0;
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sample_index=0;
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if(pfi->layer == 1)
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layer_index = 0;
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if(pfi->layer == 2)
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layer_index = 1;
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if(pfi->layer == 3)
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layer_index = 2;
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break;
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}
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if((layer_index < 0) || (layer_index > 4)) {
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pfi->is_valid=0;
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return -1;
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}
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if((sample_index < 0) || (sample_index > 2)) {
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pfi->is_valid=0;
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return -1;
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}
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if(pfi->layer==1) pfi->samples_per_frame=384;
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if(pfi->layer==2) pfi->samples_per_frame=1152;
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if(pfi->layer==3) {
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if(pfi->version == 1.0) {
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pfi->samples_per_frame=1152;
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} else {
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pfi->samples_per_frame=576;
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}
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}
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bitrate_index=(frame[2] & 0xF0) >> 4;
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samplerate_index=(frame[2] & 0x0C) >> 2;
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if(bitrate_index == 0xF) {
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pfi->is_valid=0;
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return -1;
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}
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if(samplerate_index == 3) {
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pfi->is_valid=0;
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return -1;
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}
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pfi->bitrate = scan_br_table[layer_index][bitrate_index];
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pfi->samplerate = scan_sample_table[sample_index][samplerate_index];
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if((frame[3] & 0xC0 >> 6) == 3)
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pfi->stereo = 0;
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else
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pfi->stereo = 1;
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if(frame[2] & 0x02) { /* Padding bit set */
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pfi->padding=1;
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} else {
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pfi->padding=0;
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}
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if(pfi->version == 1.0) {
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if(pfi->stereo) {
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pfi->xing_offset=32;
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} else {
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pfi->xing_offset=17;
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}
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} else {
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if(pfi->stereo) {
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pfi->xing_offset=17;
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} else {
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pfi->xing_offset=9;
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}
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}
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pfi->crc_protected=(frame[1] & 0xFE);
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if(pfi->layer == 1) {
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pfi->frame_length = (12 * pfi->bitrate * 1000 / pfi->samplerate + pfi->padding) * 4;
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} else {
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pfi->frame_length = 144 * pfi->bitrate * 1000 / pfi->samplerate + pfi->padding;
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}
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pfi->is_valid=1;
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return 0;
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}
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/*
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* scan_get_mp3fileinfo
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*
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@ -1145,26 +1293,15 @@ int scan_get_aacfileinfo(char *file, MP3FILE *pmp3) {
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int scan_get_mp3fileinfo(char *file, MP3FILE *pmp3) {
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FILE *infile;
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SCAN_ID3HEADER *pid3;
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SCAN_FRAMEINFO fi;
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unsigned int size=0;
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off_t fp_size=0;
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off_t file_size;
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unsigned char buffer[1024];
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int index;
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int layer_index;
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int sample_index;
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int ver=0;
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int layer=0;
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int bitrate=0;
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int samplerate=0;
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int stereo=0;
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int padding_bit=0;
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int padding_bytes=0;
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int samples_per_frame=0;
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int frame_size=0;
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int number_of_frames=0;
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int xing_offset,xing_flags;
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int xing_flags;
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int found;
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if(!(infile=fopen(file,"rb"))) {
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@ -1208,9 +1345,8 @@ int scan_get_mp3fileinfo(char *file, MP3FILE *pmp3) {
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index=0;
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found=0;
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if((buffer[index] == 0xFF) && (buffer[index+1] >= 224)) {
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/* good header */
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} else {
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if(scan_decode_mp3_frame(&buffer[index],&fi)) { /* Bad frame header */
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DPRINTF(E_DBG,L_SCAN,"Starting brute-force search for frame header\n");
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fp_size=0;
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@ -1233,20 +1369,16 @@ int scan_get_mp3fileinfo(char *file, MP3FILE *pmp3) {
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break; /* read in the next block */
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}
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if((buffer[index] == 0xFF) && (buffer[index+1] >= 224)) {
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DPRINTF(E_DBG,L_SCAN,"Possible header at %d\n",index);
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/* could be valid... sanity check it */
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ver=(buffer[index+1] & 0x18) >> 3;
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layer=(buffer[index+1] & 0x6) >> 1;
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bitrate=(buffer[index+2] & 0xF0) >> 4;
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if((ver != 1) && (layer != 0) && (bitrate != 0) && (bitrate !=15)) {
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DPRINTF(E_DBG,L_SCAN,"Good header\n");
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fp_size =+ (index + 1);
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if(!scan_decode_mp3_frame(&buffer[index],&fi)) {
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DPRINTF(E_DBG,L_SCAN,"valid header at %d\n",index);
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if(strncasecmp((char*)&buffer[index+fi.xing_offset+4],"XING",4) == 0) {
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found=1;
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}
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/* should check next frame... */
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found=1;
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}
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if(!found)
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index++;
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}
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@ -1267,112 +1399,31 @@ int scan_get_mp3fileinfo(char *file, MP3FILE *pmp3) {
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}
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*/
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if((buffer[index] == 0xFF)&&(buffer[index+1] >= 224)) {
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ver=(buffer[index+1] & 0x18) >> 3;
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layer=(buffer[index+1] & 0x6) >> 1;
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layer = 4-layer;
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layer_index=-1;
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sample_index=-1;
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switch(ver) {
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case 0: /* MPEG Version 2.5 */
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sample_index=2;
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if(layer == 1)
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layer_index=3;
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else
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layer_index=4;
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break;
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case 2: /* MPEG Version 2 */
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sample_index=1;
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if(layer == 1)
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layer_index=3;
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else
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layer_index=4;
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break;
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case 3: /* MPEG Version 1 */
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sample_index=0;
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if(layer == 1) /* layer 1 */
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layer_index=0;
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if(layer == 2) /* layer 2 */
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layer_index=1;
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if(layer == 3) /* layer 3 */
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layer_index=2;
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break;
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}
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if((layer_index < 0) || (layer_index > 4)) {
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DPRINTF(E_LOG,L_SCAN,"Bad mp3 header in %s: bad layer_index\n",file);
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if(scan_decode_mp3_frame(&buffer[index],&fi)) {
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fclose(infile);
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return -1;
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DPRINTF(E_DBG,L_SCAN,"Could not find sync frame\n");
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return 0;
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}
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if((sample_index < 0) || (sample_index > 2)) {
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DPRINTF(E_LOG,L_SCAN,"Bad mp3 header in %s: bad sample_index\n",file);
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fclose(infile);
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return -1;
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}
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pmp3->bitrate=fi.bitrate;
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pmp3->samplerate=fi.samplerate;
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if(layer==1) samples_per_frame=384; /* Layer I */
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if(layer==2) samples_per_frame=1152; /* Layer II */
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if(layer==3) { /* Layer III */
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if(ver == 3) { /* MPEG 1 */
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samples_per_frame=1152;
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} else {
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samples_per_frame=576;
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}
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}
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bitrate=(buffer[index+2] & 0xF0) >> 4;
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bitrate=scan_br_table[layer_index][bitrate];
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samplerate=(buffer[index+2] & 0x0C) >> 2; /* can only be 0-3 */
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samplerate=scan_sample_table[sample_index][samplerate];
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pmp3->bitrate=bitrate;
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pmp3->samplerate=samplerate;
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stereo=buffer[index+3] & 0xC0 >> 6;
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if(stereo == 3)
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stereo=0;
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else
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stereo=1;
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padding_bit=(buffer[index+2] & 0x02) >> 1;
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if(padding_bit) {
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if(layer == 1)
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padding_bytes=4;
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else
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padding_bytes=1;
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}
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DPRINTF(E_DBG,L_SCAN," MPEG Version: %s\n",ver == 3 ? "1" : (ver == 2 ? "2" : "2.5"));
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DPRINTF(E_DBG,L_SCAN," Layer: %d\n",layer);
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DPRINTF(E_DBG,L_SCAN," Sample Rate: %d\n",samplerate);
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DPRINTF(E_DBG,L_SCAN," Bit Rate: %d\n",bitrate);
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if(ver == 3) { /* MPEG 1 */
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if(stereo) {
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xing_offset=32;
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} else {
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xing_offset=17;
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}
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} else {
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if(stereo) {
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xing_offset=17;
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} else {
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xing_offset=9;
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}
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}
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DPRINTF(E_DBG,L_SCAN," MPEG Version: %0.1g\n",fi.version);
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DPRINTF(E_DBG,L_SCAN," Layer: %d\n",fi.layer);
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DPRINTF(E_DBG,L_SCAN," Sample Rate: %d\n",fi.samplerate);
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DPRINTF(E_DBG,L_SCAN," Bit Rate: %d\n",fi.bitrate);
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/* now check for an XING header */
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if(strncasecmp((char*)&buffer[index+xing_offset+4],"XING",4) == 0) {
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if(strncasecmp((char*)&buffer[index+fi.xing_offset+4],"XING",4) == 0) {
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DPRINTF(E_DBG,L_SCAN,"Found Xing header\n");
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xing_flags=*((int*)&buffer[index+xing_offset+4+4]);
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xing_flags=*((int*)&buffer[index+fi.xing_offset+4+4]);
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xing_flags=ntohs(xing_flags);
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DPRINTF(E_DBG,L_SCAN,"Xing Flags: %02X\n",xing_flags);
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if(xing_flags & 0x1) {
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/* Frames field is valid... */
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number_of_frames=*((int*)&buffer[index+xing_offset+4+8]);
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number_of_frames=*((int*)&buffer[index+fi.xing_offset+4+8]);
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number_of_frames=ntohs(number_of_frames);
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}
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}
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@ -1383,22 +1434,15 @@ int scan_get_mp3fileinfo(char *file, MP3FILE *pmp3) {
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avoid overflow */
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if(!number_of_frames) { /* not vbr */
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pmp3->song_length = (int) ((double) file_size * 8. /
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(double) bitrate);
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(double) fi.bitrate);
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} else {
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pmp3->song_length = (int) ((double)(number_of_frames*samples_per_frame*1000.)/
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(double) samplerate);
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pmp3->song_length = (int) ((double)(number_of_frames*fi.samples_per_frame*1000.)/
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(double) fi.samplerate);
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}
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}
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DPRINTF(E_DBG,L_SCAN," Song Length: %d\n",pmp3->song_length);
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} else {
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/* FIXME: should really scan forward to next sync frame */
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fclose(infile);
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DPRINTF(E_DBG,L_SCAN,"Could not find sync frame\n");
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return 0;
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}
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fclose(infile);
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return 0;
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