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Improve MPEG parser

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This commit is contained in:
bnnm 2022-05-01 18:56:52 +02:00
parent 38773bdab7
commit 1849395b8e
3 changed files with 73 additions and 40 deletions
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1
src/coding/coding.h
View File

@ -491,6 +491,7 @@ void free_mpeg(mpeg_codec_data* data);
int mpeg_get_sample_rate(mpeg_codec_data* data);
long mpeg_bytes_to_samples(long bytes, const mpeg_codec_data* data);
uint32_t mpeg_get_tag_size(STREAMFILE* sf, uint32_t offset, uint32_t header);
int mpeg_get_frame_info(STREAMFILE* sf, off_t offset, mpeg_frame_info* info);
#endif

91
src/coding/mpeg_custom_utils.c
View File

@ -340,6 +340,37 @@ int mpeg_get_frame_info(STREAMFILE* sf, off_t offset, mpeg_frame_info* info) {
return mpeg_get_frame_info_h(header, info);
}
uint32_t mpeg_get_tag_size(STREAMFILE* sf, uint32_t offset, uint32_t header) {
if (!header)
header = read_u32be(offset+0x00, sf);
/* skip ID3v2 */
if ((header & 0xFFFFFF00) == get_id32be("ID3\0")) {
size_t frame_size = 0;
uint8_t flags = read_u8(offset+0x05, sf);
/* this is how it's officially read :/ */
frame_size += read_u8(offset+0x06, sf) << 21;
frame_size += read_u8(offset+0x07, sf) << 14;
frame_size += read_u8(offset+0x08, sf) << 7;
frame_size += read_u8(offset+0x09, sf) << 0;
frame_size += 0x0a;
if (flags & 0x10) /* footer? */
frame_size += 0x0a;
return frame_size;
}
/* skip ID3v1 */
if ((header & 0xFFFFFF00) == get_id32be("TAG\0")) {
;VGM_LOG("MPEG: ID3v1 at %x\n", offset);
return 0x80;
}
return 0;
}
size_t mpeg_get_samples(STREAMFILE* sf, off_t start_offset, size_t bytes) {
off_t offset = start_offset;
off_t max_offset = start_offset + bytes;
@ -355,32 +386,13 @@ size_t mpeg_get_samples(STREAMFILE* sf, off_t start_offset, size_t bytes) {
/* MPEG may use VBR so must read all frames */
while (offset < max_offset) {
uint32_t header = read_u32be(offset+0x00, sf);
/* skip ID3v2 */
if ((header & 0xFFFFFF00) == 0x49443300) { /* "ID3\0" */
size_t frame_size = 0;
uint8_t flags = read_u8(offset+0x05, sf);
/* this is how it's officially read :/ */
frame_size += read_u8(offset+0x06, sf) << 21;
frame_size += read_u8(offset+0x07, sf) << 14;
frame_size += read_u8(offset+0x08, sf) << 7;
frame_size += read_u8(offset+0x09, sf) << 0;
frame_size += 0x0a;
if (flags & 0x10) /* footer? */
frame_size += 0x0a;
offset += frame_size;
size_t tag_size = mpeg_get_tag_size(sf, offset, header);
if (tag_size) {
offset += tag_size;
continue;
}
/* skip ID3v1 */
if ((header & 0xFFFFFF00) == 0x54414700) { /* "TAG\0" */
;VGM_LOG("MPEG: ID3v1 at %lx\n", offset);
offset += 0x80;
continue;
}
/* regular frame */
/* regular frame (assumed) */
if (!mpeg_get_frame_info_h(header, &info)) {
VGM_LOG("MPEG: unknown frame at %lx\n", offset);
break;
@ -407,28 +419,31 @@ size_t mpeg_get_samples(STREAMFILE* sf, off_t start_offset, size_t bytes) {
}
/* other flags indicate seek table and stuff */
/* vendor specific */
if (info.frame_size > xing_offset + 0x78 + 0x24 &&
read_u32be(offset + xing_offset + 0x78, sf) == 0x4C414D45) { /* "LAME" */
if (info.layer == 3) {
uint32_t delays = read_u32be(offset + xing_offset + 0x8C, sf);
encoder_delay = ((delays >> 12) & 0xFFF);
encoder_padding = ((delays >> 0) & 0xFFF);
;VGM_LOG("MPEG: found Xing header\n");
encoder_delay += (528 + 1); /* implicit MDCT decoder delay (seen in LAME source) */
if (encoder_padding > 528 + 1)
encoder_padding -= (528 + 1);
}
else {
encoder_delay = 240 + 1;
/* vendor specific */
if (info.frame_size > xing_offset + 0x78 + 0x24) {
uint32_t sub_id = read_u32be(offset + xing_offset + 0x78, sf);
if (sub_id == get_id32be("LAME") || /* LAME */
sub_id == get_id32be("Lavc")) { /* FFmpeg */
if (info.layer == 3) {
uint32_t delays = read_u32be(offset + xing_offset + 0x8C, sf);
encoder_delay = ((delays >> 12) & 0xFFF);
encoder_padding = ((delays >> 0) & 0xFFF);
encoder_delay += (528 + 1); /* implicit MDCT decoder delay (seen in LAME source) */
if (encoder_padding > 528 + 1)
encoder_padding -= (528 + 1);
}
else {
encoder_delay = 240 + 1;
}
}
/* replay gain and stuff */
}
/* there is also "iTunes" vendor with no apparent extra info, iTunes delays are in "iTunSMPB" ID3 tag */
;VGM_LOG("MPEG: found Xing header\n");
break; /* we got samples */
}
}

21
src/meta/mpeg.c
View File

@ -2,16 +2,33 @@
#include "../coding/coding.h"
/* MPEG - standard MP1/2/3 audio MP3 */
/* MPEG - standard MP1/2/3 audio */
VGMSTREAM* init_vgmstream_mpeg(STREAMFILE* sf) {
#ifdef VGM_USE_MPEG
VGMSTREAM* vgmstream = NULL;
uint32_t start_offset;
int loop_flag = 0;
mpeg_frame_info info = {0};
uint32_t header_id;
/* checks */
if (!mpeg_get_frame_info(sf, 0x00, &info))
header_id = read_u32be(0x00, sf);
if ((header_id & 0xFFF00000) != 0xFFF00000 &&
(header_id & 0xFFFFFF00) != get_id32be("ID3\0") &&
(header_id & 0xFFFFFF00) != get_id32be("TAG\0"))
goto fail;
//TODO: may try init_mpeg as-is, already skips tags
start_offset = 0x00;
while (start_offset < get_streamfile_size(sf)) {
uint32_t tag_size = mpeg_get_tag_size(sf, start_offset, 0);
if (tag_size == 0)
break;
start_offset += tag_size;
}
if (!mpeg_get_frame_info(sf, start_offset, &info))
goto fail;
/* .mp3/mp2: standard (is .mp1 ever used in games?)