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d54492cb95
To support future MPEGs of uncertain layout and frame variations (namely EALayer3) the code has been restructured: mpeg_decoder does stream procesing and decoding, while mpeg_custom_utils_x does init and parsing (write to data buffer + update offsets), per MPEG subtype. Internals have changed but still gives byte-exact results. AHX has been adapted to this format as a test. Some modes (P3D/EALayer3/LyN/AWC) are defined for later development but will fail on init ATM.
67 lines
2.4 KiB
C
67 lines
2.4 KiB
C
#include "mpeg_decoder.h"
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#ifdef VGM_USE_MPEG
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#define MPEG_AHX_EXPECTED_FRAME_SIZE 0x414
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/* writes data to the buffer and moves offsets, transforming AHX frames as needed */
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int mpeg_custom_parse_frame_ahx(VGMSTREAMCHANNEL *stream, mpeg_codec_data *data) {
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/* 0xFFF5E0C0 header: frame size 0x414 (160kbps, 22050Hz) but they actually are much shorter */
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size_t current_data_size = 0;
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size_t file_size = get_streamfile_size(stream->streamfile);
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/* find actual frame size by looking for the next frame header */
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{
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uint32_t current_header = (uint32_t)read_32bitBE(stream->offset, stream->streamfile);
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off_t next_offset = 0x04;
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while (next_offset <= MPEG_AHX_EXPECTED_FRAME_SIZE) {
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uint32_t next_header = (uint32_t)read_32bitBE(stream->offset + next_offset, stream->streamfile);
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if (current_header == next_header) {
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current_data_size = next_offset;
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break;
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}
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/* AHXs end in a 0x0c footer (0x41485845 0x28632943 0x52490000 / "AHXE" "(c)C" "RI\0\0") */
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if (stream->offset + next_offset + 0x0c >= file_size) {
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current_data_size = next_offset;
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break;
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}
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next_offset++;
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}
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}
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if (!current_data_size || current_data_size > data->buffer_size || current_data_size > MPEG_AHX_EXPECTED_FRAME_SIZE) {
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VGM_LOG("MPEG AHX: incorrect data_size 0x%x\n", current_data_size);
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goto fail;
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}
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/* read VBR frames with CBR header, 0-fill up to expected size to keep mpg123 happy */
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data->bytes_in_buffer = read_streamfile(data->buffer,stream->offset,current_data_size,stream->streamfile);
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memset(data->buffer + data->bytes_in_buffer,0, MPEG_AHX_EXPECTED_FRAME_SIZE - data->bytes_in_buffer);
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data->bytes_in_buffer = MPEG_AHX_EXPECTED_FRAME_SIZE;
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/* encryption 0x08 modifies a few bits in the side_data every frame, here we decrypt the buffer */
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if (data->config.encryption) {
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VGM_LOG("MPEG AHX: unknown encryption\n");
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goto fail;
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}
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/* update offsets */
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stream->offset += current_data_size;
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if (stream->offset + 0x0c >= file_size)
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stream->offset = file_size; /* move after 0x0c footer to reach EOF (shouldn't happen normally) */
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return 1;
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fail:
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return 0;
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}
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#endif
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