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vdr-plugin-femon/femonaac.c

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/*
* Frontend Status Monitor plugin for the Video Disk Recorder
*
* See the README file for copyright information and how to reach the author.
*
*/
#include "femontools.h"
#include "femonaac.h"
#define IS_HEAAC_AUDIO(buf) (((buf)[0] == 0xFF) && (((buf)[1] & 0xF6) == 0xF0))
static unsigned int samplerates[16] =
{
96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, -1, -1, -1, -1
};
bool getAACAudioInfo(uint8_t *buf, int len, audio_info_t *info)
{
// HE-AAC audio detection, search for syncword with layer set to 0
if ((len < 4) || !IS_HEAAC_AUDIO(buf))
return false;
/* ADTS Fixed Header:
* syncword 12b always: '111111111111'
* id 1b 0: MPEG-4, 1: MPEG-2
* layer 2b always: '00'
* protection_absent 1b
* profile 2b 0: Main profile AAC MAIN 1: Low Complexity profile (LC) AAC LC 2: Scalable Sample Rate profile (SSR) AAC SSR 3: (reserved) AAC LTP
* sampling_frequency_index 4b
* private_bit 1b
* channel_configuration 3b
* original/copy 1b
* home 1b
* emphasis 2b only if ID == 0 (ie MPEG-4)
*/
int sampling_frequency_index = (buf[2] & 0x03C) >> 2;
int channel_configuration = ((buf[2] & 0x01) << 2) | ((buf[3] & 0xC0) >> 6);
info->codec = AUDIO_CODEC_HEAAC;
info->bitrate = AUDIO_BITRATE_RESERVED;
switch (channel_configuration) {
case 0:
info->channelMode = AUDIO_CHANNEL_MODE_STEREO;
break;
case 1:
info->channelMode = AUDIO_CHANNEL_MODE_JOINT_STEREO;
break;
case 2:
info->channelMode = AUDIO_CHANNEL_MODE_DUAL;
break;
case 3:
info->channelMode = AUDIO_CHANNEL_MODE_SINGLE;
break;
default:
info->channelMode = AUDIO_CHANNEL_MODE_INVALID;
break;
}
switch (sampling_frequency_index) {
case 0xC ... 0xF:
info->samplingFrequency = AUDIO_SAMPLING_FREQUENCY_RESERVED;
break;
default:
info->samplingFrequency = samplerates[sampling_frequency_index];
break;
}
return true;
}