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mpa_header.c
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mpa_header.c
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/*
* MPEG Audio Header Parser
* and rudimentary AC-3 Audio Header Parser
*
* Copyright (C) 2006 Nicholas J. Humfrey
* Copyright (C) 2018-2021 Carsten Groß
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/*
MPEG Audio frame handling courtesy of Scott Manley
Borrowed from libshout 2.1 / mp3.c
With a few changes and fixes
*/
#include <stdio.h>
#include <stdlib.h>
#include "ts2shout.h"
#include "mpa_header.h"
#include "rds.h"
extern programm_info_t *global_state;
#define MPA_MODE_STEREO 0
#define MPA_MODE_JOINT 1
#define MPA_MODE_DUAL 2
#define MPA_MODE_MONO 3
static const unsigned int mp2_bitrate[4][4][16] =
{
{ // MPEG 2.5
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // Layer 4 (does not exist)
{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, // Layer 3
{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, // Layer 2
{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0} // Layer 1
},
/* Nix ... reserved */
{ // MPEG 2.5
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // Layer 4 (does not exist)
{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, // Layer 3
{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, // Layer 2
{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0} // Layer 1
},
{ // MPEG 2
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // Layer 4 (does not exist)
{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, // Layer 3
{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, // Layer 2
{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0} // Layer 1
},
{ // MPEG 1
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // Layer 4 (does not exist)
{0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0}, // Layer 3
{0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0}, // Layer 2
{0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0} // Layer 1
},
};
static const unsigned int mp2_samplerate[4][4] =
{
{ 11025, 12000, 8000, 0 }, // MPEG 2.5
{ 0, 0, 0, 0 }, // Nix
{ 22050, 24000, 16000, 0 }, // MPEG 2
{ 44100, 48000, 32000, 0 }, // MPEG 1
};
/* Stuff for AAC */
/* See https://github.com/mvaneerde/blog/blob/master/scripts/adtsaudioheader.pl */
static const unsigned aac_samplerate[] = {
96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350, 0, 0, 0 };
static const char * aac_channel_name[] = {
"Unknown", "C (1/0)", "L/R (2/0)", "L/C/R (3/0)", "L/C/R/S (4/0)",
"L/C/R/LS/RS (5/0)" , "L/C/R/LS/RS/LFE (5/1)", "L/C/R/LS/RS/LF/RF/LFE (7/1)"};
// static const char * aac_sub_profile_name[] = {
// "Main", "Low complexity", "scaleable sampling rate", "reserved" };
/* new definitions for AC3
* from http://stnsoft.com/DVD/ac3hdr.html */
static const unsigned int ac3_samplerate[4] = { 48000,44100,32000,0 };
static const unsigned int ac3_bitrate[] = {
32, 32, 40, 40, 48, 48, 56, 56, /* value 0 - 7 */
64, 64, 80, 80, 96, 96,112,112, /* value 8 - 15 */
128,128,160,160,192,192,224,224, /* value 16 - 23 */
256,256,320,320,384,384,448,448, /* value 24 - 31 */
512,512,576,576,640,640,0, 0, /* value 32 - 39 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* value 40 - 55 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 /* value 56 - 63 */
};
static const unsigned int ac3_channels[] = {
2,1,2,3,3,4,4,5,0,0,0
};
static const char *ac3_channel_name[] = {
"Ch1/Ch2 (1+1)", "C (1/0)", "L/R (2/0)", "L/C/R (3/0)", "L/R/S (2/1)",
"L/C/R/S (3/1)", "L/R/SL/SR (2/2)", "L/C/R/SL/SR (3/2)" };
/* We use the advantage that we already know wether we get
* AAC or MPEG. We know this from the PMT */
static void parse_header(const unsigned char* buf, mpa_header_t *mh, u_int32_t header)
{
mh->syncword = (header >> 20) & 0x0fff;
/* This is for the RDS scan, makes detection of frame header more robust */
mh->sync0 = (header>>24) & 0xff;
mh->sync1 = (header>>16) & 0xff;
mh->sync2 = (header>>8) & 0xff;
mh->sync3 = (header) & 0xff;
/* I changed to map it directly to ease AAC/MPEG handling */
mh->version = (header >> 18) & 0x03;
mh->layer = (header >> 17) & 0x03;
/* The stream type is set via the flags from the PMT */
if (global_state->stream_type == STREAM_MODE_AAC) {
if (mh->version == 0 && mh->layer == 0) {
/* AAC / ADTS */
mh->samplerate_index = (header>>12) & 0x0f;
mh->samplerate = aac_samplerate[mh->samplerate_index];
mh->channel_acmod = (header>>6) & 0x7;
/* TODO Oergs.. we have to set something until we implement fetching bitrate for AAC */
mh->bitrate = 16;
global_state->sr = mh->samplerate;
global_state->br = mh->bitrate;
}
} else if ( global_state->stream_type == STREAM_MODE_AACP) {
/* AAC / HE-AAC / COMPLEX / LATM/LOAS */
/* AAC LATM is protected with a huge amount of software patents.
* Transport in mp2t is without ADTS header. In theory the parameters are
* transported in PMT, but it's only decodeable with a library like ffmpeg. Therefore we match on
* mp4 / aac raw frame-beginnings and reverse engineer the parameters in PMT AAC descriptor 0x7c */
if (buf[0] == 0x56 && ((buf[1] & 0xfe) == 0xe0) ) {
// unsigned int profile = 0;
#ifdef DEBUG
fprintf(stderr, "---------------------- HE-ACC found valid syncword ----------------------------\n");
DumpHex((unsigned char*)buf, 4);
#endif
/* No layer and version info */
mh->layer = 0;
mh->version = 0;
/* LATM gives SR and BR in meta info, not in stream itself */
mh->samplerate = global_state->sr;
/* If Bitrate is coming from DVB information (PMT) use it from there */
if (global_state->br == 0 ) {
global_state->br = mh->bitrate;
}
}
} else if (global_state->stream_type == STREAM_MODE_MPEG) {
if (mh->version != 0 && mh->layer != 0) {
mh->error_protection = ((header >> 16) & 0x01) ? 0 : 1;
mh->bitrate_index = (header >> 12) & 0x0F;
mh->samplerate_index = (header >> 10) & 0x03;
mh->padding = (header >> 9) & 0x01;
mh->extension = (header >> 8) & 0x01;
mh->mode = (header >> 6) & 0x03;
mh->mode_ext = (header >> 4) & 0x03;
mh->copyright = (header >> 3) & 0x01;
mh->original = (header >> 2) & 0x01;
mh->emphasis = header & 0x03;
mh->bitrate = mp2_bitrate[mh->version][mh->layer][mh->bitrate_index];
// fprintf(stderr, "Accessed bitrate: %d, with version %d, Layer %d, bitrate_index %d\n", mh->bitrate, mh->version, mh->layer, mh->bitrate_index);
mh->samplerate = mp2_samplerate[mh->version][mh->samplerate_index];
// fprintf(stderr, "Accessed samplerate: %d, with version %d, samplerate_index %d\n", mh->samplerate, mh->version, mh->samplerate_index);
/* also set global stuff */
global_state->br = mh->bitrate;
global_state->sr = mh->samplerate;
}
} else {
mh->bitrate = 0;
mh->samplerate = 0;
}
if (mh->mode == MPA_MODE_MONO)
mh->channels = 1;
else
mh->channels = 2;
if (mh->version == 1)
mh->samples = 1152;
else
mh->samples = 576;
if(mh->samplerate)
mh->framesize = (mh->samples * mh->bitrate * 1000 / mh->samplerate) / 8 + mh->padding;
}
// concise informational string
void mpa_header_print( mpa_header_t *mh )
{
char mpeg_std[20];
char mpeg_mode[20];
if (global_state->stream_type == STREAM_MODE_MPEG) {
if (mh->version==3) sprintf(mpeg_std, "MPEG-1");
else if (mh->version==2) sprintf(mpeg_std, "MPEG-2");
else if (mh->version==1) sprintf(mpeg_std, "MPEG-Unknown");
else if (mh->version == 0) sprintf(mpeg_std, "MPEG-2.5");
if (mh->mode==MPA_MODE_STEREO) sprintf(mpeg_mode, "Stereo");
else if (mh->mode==MPA_MODE_JOINT) sprintf(mpeg_mode, "Joint Stereo");
else if (mh->mode==MPA_MODE_DUAL) sprintf(mpeg_mode, "Dual");
else if (mh->mode==MPA_MODE_MONO) sprintf(mpeg_mode, "Mono");
output_logmessage("Synced to %s layer %d, %d kbps, %d Hz, %s\n", mpeg_std, mh->layer, mh->bitrate, mh->samplerate, mpeg_mode);
} else if ( global_state->stream_type == STREAM_MODE_AAC ) {
if (mh->version == 0 && mh->layer == 0) {
output_logmessage("Synced to AAC audio, Samplerate %d Hz, Configuration: %s\n", mh->samplerate, aac_channel_name[mh->channel_acmod]);
}
} else if ( global_state->stream_type == STREAM_MODE_AACP ) {
if ( mh->layer == 0 ) {
output_logmessage("Synced to LATM audio, Guessed Samplerate %d Hz, Bitrate %d kBit/s\n", global_state->sr, global_state->br);
}
}
}
void ac3_header_print (mpa_header_t *mh)
{
output_logmessage("Synced to AC-3, %d kbit/s, %d Hz, channels: %s\n", mh->bitrate, mh->samplerate, ac3_channel_name[mh->channel_acmod]);
}
// Parse mpeg audio header
// returns 1 if valid, or 0 if invalid
int mpa_header_parse( const unsigned char* buf, mpa_header_t *mh)
{
u_int32_t head;
/* Quick check */
if (global_state->stream_type != STREAM_MODE_AACP && buf[0] != 0xFF)
return 0;
/* Put the first four bytes into an integer */
head = ((u_int32_t)buf[0] << 24) |
((u_int32_t)buf[1] << 16) |
((u_int32_t)buf[2] << 8) |
((u_int32_t)buf[3]);
/* fill out the header struct */
parse_header(buf, mh, head);
/* Sanity checks for MPEG1/2 */
if (global_state->stream_type == STREAM_MODE_MPEG) {
/* check for syncword */
if ((mh->syncword & 0x0ffe) != 0x0ffe)
return 0;
/* make sure layer is sane */
if (mh->layer == 0 && mh->version != 0)
return 0;
/* make sure version is sane */
if (mh->version == 0 && mh->layer != 0)
return 0;
/* make sure bitrate is sane */
if (mh->bitrate == 0)
return 0;
/* make sure samplerate is sane */
if (mh->samplerate == 0)
return 0;
return 1;
} else {
#ifdef DEBUG
DumpHex((unsigned char*)buf, 4);
#endif
if (global_state->stream_type != STREAM_MODE_AACP && (mh->syncword & 0x0fff) != 0xfff)
return 0;
if (mh->layer > 0)
return 0;
if (mh->samplerate == 0)
return 0;
return 1;
}
}
// Parse AC-3 Audio header
// returns 1 if valid, or 0 if invalid
// Header info found at http://stnsoft.com/DVD/ac3hdr.html#bsmod
int ac3_header_parse( const unsigned char* buf, mpa_header_t *mh)
{
// u_int16_t crc16;
/* Quick check */
if (buf[0] != 0x0b)
return 0;
if (buf[1] != 0x77)
return 0;
/* Put the first four bytes into an integer */
// crc16 = (u_int16_t)buf[2]<<8 | (u_int16_t)buf[3];
mh->samplerate = ac3_samplerate[((buf[4] >>6)&0x3)];
mh->bitrate = ac3_bitrate[(buf[4]&0x3f)];
mh->version = buf[5]>>3;
mh->channel_acmod = buf[6]>>5;
mh->channels = ac3_channels[mh->channel_acmod];
/* make sure version is sane */
if (mh->version == 0)
return 0;
/* make sure bitrate is sane */
if (mh->bitrate == 0)
return 0;
/* make sure samplerate is sane */
if (mh->samplerate == 0)
return 0;
/* sane values are given, set them */
global_state->br = mh->bitrate;
global_state->sr = mh->samplerate;
return 1;
}