hash stringlengths 32 32 | doc_id stringlengths 7 13 | section stringlengths 3 121 | content stringlengths 0 2.2M |
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79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.7 b_codecdata - codec specific data flag | This Boolean indicates whether codec-specific data is included in the payload configuration. Otherwise, the payload configuration data conforms to the present document. |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.8 codecdata - codec specific data | This 8-bit element is not specified here since bitstreams that conform to the present document shall have a value of false for b_codecdata. |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.9 b_discard_unknown_payload - discard unknown payload during transcode flag | This Boolean indicates whether the current payload is retained or discarded during a transcoding process, if the transcoder does not recognize the specific emdf_payload_id value of the payload. ETSI ETSI TS 103 190-1 V1.4.1 (2025-07) 136 In this case, the current payload shall be discarded during a transcoding process ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.10 b_payload_frame_aligned - payload to audio data frame alignment flag | This Boolean indicates how closely the payload data and the audio data within the AC-4 frame need to be synchronized after decoding and/or during transcoding. In this case, the payload data shall be applied to the decoded audio from that AC-4 frame. Otherwise, the application of the payload data to the decoded audio fr... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.11 b_create_duplicate - create duplicate payload during transcode flag | In some transcoding operations, the frame length of the output format may be shorter than the length of an AC-4 frame. This Boolean indicates whether the payload shall be repeated in all frames of the output format that correspond to the same period of time as the current AC-4 frame. Otherwise, the payload does not nee... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.12 b_remove_duplicate - remove duplicate payload during transcode flag | This Boolean indicates whether payloads with the same emdf_payload_id value as the current payload need to be included only once in every output frame of the transcoding process when the output frame duration of a transcoding process is longer than the duration of an AC-4 frame. In this case, subsequent payloads carrie... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.13 priority - payload priority | This 5-bit element is used to indicate the priority of this payload in relation to other payloads in the EMDF substream. This field may be used to indicate whether a payload can be discarded during a transcoding process to a lower data rate output format that is not able to support all payloads. A priority value of 0 i... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.2.14 proc_allowed - processing allowed | This 2-bit element is used to indicate whether a payload should be retained or discarded during transcoding if processing is applied to the metadata and/or audio data decoded from the AC-4 frame during transcoding. The value of the proc_allowed field shall be set as shown in table 175. Table 175: Meaning of proc_allowe... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.3 emdf_reserved - EMDF reserved data | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.3.1 n_skip_bytes_length_primary - length of reserved bytes | This element indicates if reserved bytes are present. If present and not zero, the number n_skip_bytes of bytes to skip is incremented by 2×_ __ _ . |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.3.2 n_skip_bytes_length_secondary - length of reserved bytes | This element indicates if reserved bytes are present. If present and not zero, the number n_skip_bytes of bytes to skip is incremented by 2×_ __ _ . |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.15.3.3 reserved - Reserved | This element is reserved for future use and the content shall be skipped by an AC-4 decoder conforming to the present document. |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 4.3.16 High sampling frequency - HSF | 4.3.16.1 max_sfb_hsf_ext[i] - HSF extension for number of transmitted scale factor bands for index i This element indicates the number of scale factor bands to be added to the number of scale factor bands transmitted in asf_psy_info to calculate the total number of scale factor bands max_sfb_hsf in the high sampling fr... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5 Algorithmic details | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1 Audio spectral frontend | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.1 Introduction | The audio spectral front end tool is one of two spectral frontend tools that are used to create spectral lines of audio tracks from sf_data() elements in an AC-4 frame. These spectral lines are typically routed through the stereo and multichannel processing tool before being routed into the Inverse Modified Discrete Co... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.2 Entropy coding of spectral values | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.2.1 Data and control interfaces | The input to the Huffman decoding tool is the asf_spectral_data() part of an sf_data() element: • spectral_data Huffman coded spectral data (collection of Huffman codewords and sign bits). The length of the spectral data is only known after the Huffman decoding process. The output from the Huffman decoding tool is a ve... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.2.2 Decoding process | The quantized spectral lines are stored as Huffman encoded values in the bitstream. To retrieve the quantized spectral lines, Huffman decoding shall be applied. For each Huffman codeword in the bitstream, the used Huffman codebook number sect_cb[g][s] is known from the section data. All the valid Huffman codebooks for ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.3 Quantization reconstruction and scaling | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.3.1 Data and control interfaces | The input to the quantization reconstruction and scaling tool is a vector of quantized spectral lines and the asf_scalefac_data() part of an sf_data() element: • quant_spec Vector of quantized spectral lines. NOTE 1: The maximum allowed value of the elements of quant_spec is 8 191. • scale_factor_data Huffman-coded sca... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.3.2 Decoding process | To convert the quantized spectral lines into scaled spectral lines, a quantization reconstruction and scaling step shall be applied. The following (non-uniform) reconstruction process shall be used to apply the inverse operation to the non-uniform quantization operation used by the encoder for the spectral lines. The r... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.4 Spectral noise fill | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.4.1 Data and control interfaces | The input to and the output from the spectral noise fill tool is a vector of spectral lines in bitstream order: • scaled_spec Vector of (scaled) spectral lines in bitstream order. The bitstream parameter and helper elements used by the spectral noise fill tool are: • num_window_groups Number of window groups. NOTE 1: T... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.4.2 Decoding process | Spectral lines in scaled_spec that are 0 because either the corresponding sfb_cb[g][sfb] is 0 or the corresponding max_quant_idx[g][sfb] is 0 shall be replaced by random noise of a transmitted level if noise fill data is present as indicated when b_snf_data_exists is false. If b_snf_data_exists is false, the spectral n... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.5 Spectral ungrouping tool | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.5.1 Data and control interfaces | The input to the ungrouping tool is a vector of spectral lines in bitstream order: ETSI ETSI TS 103 190-1 V1.4.1 (2025-07) 146 • scaled_spec Vector of (scaled) spectral lines in bitstream order. The output from the ungrouping tool is a vector of reordered spectral lines: • spec_reord Vector of reordered (scaled) spectr... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.1.5.2 Decoding process | When more than one transform block is used in an AC-4 frame, spectral lines are stored in groups. To undo this grouping, the AC-4 decoder shall apply reordering as specified in the following pseudocode. Pseudocode 25 k = 0; win = 0; spec_reord[] = 0; /* init all spectral lines with 0 */ for (g = 0; g < num_window_group... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2 Speech spectral frontend | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.1 Introduction | The speech spectral front end is an alternative spectral frontend to the audio spectral front end. It is designed to be used for speech content. Like the audio spectral front end, the speech spectral front end provides blocks of spectral lines that need to be inverse transformed using the same inverse MDCT as for the a... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.2 Top level structure of the SSF | Figure 4: SSF decoder block diagram Figure 4 shows the SSF decoder block diagram. The predictor decoder, the spectrum decoder and the envelope decoder take bitstream elements as input. The output of the spectrum decoder is combined (added) with the output of the subband predictor and sent to the inverse flattening whic... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.3 Envelope decoder | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.3.0 Data and control interfaces | The input to the envelope decoder is a vector of envelope indices, a vector of gain indices and a vector decoded envelope values from the previous frame: • env_idx[band] Vector of num_bands envelope indices. NOTE 1: The first index describes an independently coded value of the first band while the remaining indices des... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.3.0a Envelope decoding | Pseudocode 4a: Decoding of env_idx[band] into env[band] // decode envelope ENV_DELTA_MIN = -16; ENV_BAND0_MIN = -28; ETSI ETSI TS 103 190-1 V1.4.1 (2025-07) 149 env[0] = env_idx[0] + ENV_BAND0_MIN; for (band = 1; band < num_bands; band++) { delta = env_idx[band] + ENV_DELTA_MIN; env[band] = env[band-1] + delta; } NOTE:... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.3.0b Envelope interpolation | For the SHORT_STRIDE mode, envelope interpolation shall be done. For the LONG_STRIDE mode, no interpolation is needed and env_interp[0][band] = env[band]. The envelope interpolation is described in the following pseudocode. Pseudocode 4b // interpolate envelope (SHORT_STRIDE) const int32 iUnit = 1024; /* Q.10 */ const ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.3.0c Gain decoding | For the SHORT_STRIDE mode, gain indices are transmitted for each of the four blocks. The following pseudocode shows how the gain indices are converted into gains. Pseudocode 4c: Decoding of gain_idx[block] into gain[block] // gain_idx to gain conversion for (block = 0; block < 4; block++) { gain[block] = pow(10.0f, gai... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.3.0d Envelope refinement | Pseudocode 4d SSF_HIGH_FREQ_GAIN_THRESHOLD = 2; ENV_MIN = -64; ENV_MAX = 63; // signal envelope for (block = 0; block < num_blocks; block++) { for (band = 0; band < num_bands; band++) { // envelope reconstruction f_env_signal[block][band] = pow(2.0f, 0.5f * env_interp[block][band]); if (band >= SSF_HIGH_FREQ_GAIN_THRES... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.4 Predictor decoder | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.4.0 Data and control interfaces | The inputs to the predictor decoder are SSF bitstream elements. The outputs from the predictor decoder are the following predictor parameters: • f_pred_gain[block] Vector of num_blocks predictor gain values. • f_pred_lag[block] Vector of num_blocks predictor lag values. The state internal to the predictor decoder is th... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.4.0a Parameter calculation | Pseudocode 4e // decode predictor parameters for block index block PRED_LAG_DELTA_MIN = -8; if ((block >= start_block) && (block < end_block)) { // predictor parameters are possible if (predictor_presence_flag[block] == 1) { i_pred_gain_idx[block] = arithmetic_decode_pred(); // reconstruct f_pred_gain[block] = PRED_GAI... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5 Spectrum decoder | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.1 Spectrum decoder: Data and control interfaces | The inputs to the spectrum decoder are envelope allocation values and the predictor gain for the current block: • env_alloc[band] Vector of num_bands envelope allocation values (integer) for current block. • f_pred_gain Predictor gain value for the current block. • block Block index of the current block. The output fro... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2 Spectrum decoding process | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2.0 Introduction | The process of spectrum decoding comprises the following steps: 1) Helper variable calculation The helper variables f_rfu, i_alloc_dithering_threshold, f_adaptive_noise_gain and f_adaptive_noise_gain_var_pres are calculated for the current block. See the pseudocode example in clause 5.2.5.2.1. 2) Heuristic scaling and ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2.1 Helper variable calculation | This pseudocode demonstrates how helper variables f_rfu, i_alloc_dithering_threshold, f_adaptive_noise_gain and f_adaptive_noise_gain_var_pres are calculated for the current block. Pseudocode 26 // compute helper variables f_rfu, i_alloc_dithering_threshold, f_adaptive_noise_gain // and f_adaptive_noise_gain_var_pres f... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2.2 Heuristic scaling and envelope allocation modification | The pseudocode examples in this clause demonstrate the calculaton of heuristic scaling and envelope allocation modification when f_rfu is >0 and variance_preserving_flag is 0. Pseudocode 27 // Heuristic scaling and envelope allocation modification ENV_MIN = -64; ENV_MAX = 63; for (band = 0; band < num_bands; band++) { ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2.3 Lossless decoding | This pseudocode demonstrates the lossless decoding process. Pseudocode 31 // Lossless decoding MIN_ALLOC_OFFSET = -21; ENV_MAX_2_MIN_OFFSET = 20; i_alloc_offset = alloc_offset_bits + MIN_ALLOC_OFFSET; // find max entry in env_alloc_mod[band] i_max = env_alloc_mod[0]; for (band = 1; band < num_bands; band++) { if (env_a... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2.4 Inverse quantization | The inverse quantization process is shown in the following pseudocode. Pseudocode 32 // Inverse quantization (for block index block) /* important variables for bit-exact processing */ int32 i_step_size, i_mid_point, i_dither, i_quant_index; const int32 i_model_unit = (1U << 15); for (band = 0; band < num_bands; band++)... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.5.2.5 Application of heuristic inverse scaling | Heuristic inverse scaling, as shown the following pseudocode, shall be applied if variance_preserving_flag is 0. Pseudocode 34 // Heuristic inverse scaling for (band = 0; band < num_bands; band++) { f_gain_value = 1.0f / f_gain_q[band]; for (bin = start_bin[band] ; bin <= end_bin[band]; bin++) { f_spec_res[bin] = f_spe... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.6 Subband predictor | Data and Control Interfaces The input to the subband predictor is a vector of SSF output spectral lines from the previous block, a signal envelope vector for the current block, and the predictor parameters from the predictor decoder for the current block: • f_spec[bin] Vector of num_bins spectral lines from the previou... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.7 Inverse flattening | Data and control interfaces The input to the inverse flattening is the spectrum from the spectrum decoder, the spectrum from the subband predictor, and the signal envelope values for the current block: • f_spec_res[bin] Vector of num_bins residual spectral lines from the spectrum decoder. • f_spec_pred[bin] Vector of n... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.8 Parameterization | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.8.1 C matrix | The extractor of the subband predictor uses a matrix C, selected by tab_idx. The setup of all 37 possible matrices, stored in a big table C_ALL[tab_idx], is described in the following pseudocode. Each matrix C is a three-dimensional array of prediction coefficients of the size (2Rf + 1)×65×Rt, where Rt and Rf are depen... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.8.2 Arithmetic coding | A single instance of an arithmetic coder is used during the arithmetic decoding of the following three parameter types within an SSF granule, each using a different statistical model: • envelope indices using a static pre-trained Cumulative Distribution Function (CDF) table; • predictor gain indices using a static pre-... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.2.8.3 Dither and random noise | Two instances of a random number generator are used during the SSF decoding: one for the dither signal setup and the other one for noise signal values. The implementation of the random number generator shall conform to the code in the following pseudocode since it is important that the SSF encoder and the SSF decoder u... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3 Stereo and multichannel processing | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.1 Introduction | The multichannel tools take their input from one or more spectral frontends, receiving n-tuples of spectra with matching time/frequency layout. The multichannel processing tool applies a number time-varying and frequency-varying matrix operation on these tuples. Between two and seven spectra are transformed at a time. ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.2 Parameter extraction | All parameters for the multichannel tool are transmitted in one or more chparam_info() elements. The following pseudocode describes parsing the chparam_info() element and extracting parameters a, b, c, d. Pseudocode 59 // initialize a[g][sfb], b[g][sfb], c[g][sfb] and d[g][sfb] after parsing of // chparam_info() max_sf... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3 Processing the channel data elements | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3.0 Introduction | In the various channel data elements, a number n > 1 of input tracks (I0, …, In) are matrix transformed into the n output tracks (O0, …, On). They share the same sf_info and so share the same time/frequency resolution. The matrix equations below are understood to apply to each time/frequency tile separately, with separ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3.1 Processing tracks of the mono_data element | Let I0 be the track decoded from the sf_data element contained in the mono_data element. The decoder shall map the input track directly to the output O0, i.e.: O = I |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3.2 Processing tracks of the two_channel_data or stereo_data element | Let I0 and I1 be the tracks decoded from the two sf_data elements contained in the two_channel_data element, or of the stereo_data element. If b_enable_mdct_stereo_proc is false, no further processing is necessary and O0=I0, O1=I1. Otherwise, the decoder shall extract the parameters a, b, c, d from the contained chpara... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3.3 Processing tracks of the three_channel_data element | Let I0, I1, and I2 be the tracks decoded from the three sf_data elements contained in the three_channel_data element. The decoder shall extract parameters a i, b i, c i, d i (i = 0…1) from the two contained chparam_info elements, and from the chel_matsel element determine the transform matrix M as described in table 17... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3.4 Processing tracks of the four_channel_data element | Let I0…I3 be the tracks decoded from the four sf_data elements contained in the four_channel_data element. The decoder shall extract parameters ai, bi, ci, di (i = 0…3) from the four contained chparam_info elements. Finally, the output tracks O0… O3 shall be derived by: + O O O O , = + a a b a a b b b c a d a... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.3.5 Processing tracks of the five_channel_data element | Let I0…I4 be the tracks decoded from the five sf_data elements contained in the five_channel_data element. Next the decoder shall extract parameters ai, bi, ci, di (i = 0…4) from the five contained chparam_info elements, and from the chel_matsel element determine the transform matrix M as described in table 179. Finall... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4 Processing the channel elements | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.0 Introduction | Tracks routed into the stereo and multiprocessing tool (sSMP,%0|1|2&… ') may originate from four different channel elements: channel_pair_element, 3_0_channel_element, 5_X_channel_element or 7_X_channel_element. Processing and mapping from input tracks to output channels (sSMP,%L|R|C&… ') differs depending on the chann... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.1 Processing tracks of a channel_pair_element | If stereo_codec_mode {SIMPLE,ASPX,ASPX_ACPL_1}, the 2 tracks of the stereo_data() element shall be processed according to clause 5.3.3.2. The mapping of input tracks and output channels shall be done as follows: %I I& = 'sSMP, sSMP,( %SSMP,L sSMP,R& = %O O& If stereo_codec_mode = ASPX_ACPL_2, the single track of t... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.2 Processing tracks of a 3_0_channel_element | If 3_0_coding_config = 0, the 2 tracks of the stereo_data() element (sSMP,0, sSMP,1) are processed according to clause 5.3.3.2. The mapping of input tracks and output channels shall be done as follows: I I = sSMP, sSMP, SSMP,L sSMP,R = O O The third track of the additional mono_data() element, sSMP,2, shall ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.3 Processing tracks of a 5_X_channel_element | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.3.0 Introduction | The up to 5 tracks acquired from a 5_X_channel_element shall be processed according to the channel data element they originate from. Tables in this clause describe which tracks shall be taken as input, and which channels are produced as output when processing the various channel data elements according to clause 5.3.3.... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.3.3 5_X_codec_mode = ASPX_ACPL_3 | If 5_X_codec_mode = ASPX_ACPL_3, the two audio tracks (sSMP,0, sSMP,1) are acquired from a stereo_data element and processed according to clause 5.3.3.2. The mapping of input tracks and output channels shall be done as follows: I I = sSMP, sSMP, ⎣ ⎢ ⎢ ⎢ ⎡SSMP,L sSMP,R sSMP,C sSMP,Ls sSMP,Rs⎦ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎡1 ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.4 Processing tracks of the 7_X_channel_element | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.4.0 Introduction | The 7_X_channel_element enables the decoder for two more channels beyond L, R, C, Ls and Rs (refer to table 88 for details). Analogously to the 5_X_channel_element, up to 7 tracks of a 7_X_channel_element shall be processed according to the channel data element from which they originate. Table notations are borrowed fr... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.4.2 7_X_codec_mode = ASPX_ACPL_1 | If 7_X_codec_mode = ASPX_ACPL_1, seven audio tracks are available. Processing is done analogously to the case when 7_X_codec_mode = SIMPLE and b_use_sap_add_ch is false, with the difference that the output channels F and G are derived from two sf_data elements and their associated chparam_info elements instead of the t... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.3.4.4.3 7_X_codec_mode = ASPX_ACPL_2 | If 7_X_codec_mode = ASPX_ACPL_2, five audio tracks are available. The mapping of input tracks and preliminary output channel descriptors (A,B,D,E,F,G) is described in table 184. The processing for each of the channel data elements shall be done according to clause 5.3.3.0. Table 184: Input and preliminary output mappin... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.4 96 and 192 kHz decoding | The Boolean b_hsf_ext indicates whether the ac4_hsf_ext_substream structure contains further spectral data, scalefactor data and spectral noise fill data extending the data beyond 24 kHz. If the decoder is not capable of decoding into 96 kHz or 192 kHz output, it shall ignore the additional coefficients. If the decoder... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.5 IMDCT equations and block switching | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.5.1 Introduction | The choice of analysis block length is fundamental to any transform-based audio coding system. A long transform length is most suitable for input signals whose spectrum remains stationary, or varies only slowly, with time. A long transform length also provides greater frequency resolution, and hence improved coding per... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.5.2 Transforms | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.5.2.1 Data and control interfaces | The IMDCT applies the inverse of the frequency mapping that was carried out in the encoder. See clause 5.5.3 for a full list of supported transform lengths. The input to the IMDCT is a block of N scaled spectral lines: • sIMDCT,ch Vector of N spectral lines of channel ch. The output from the IMDCT and the overlap/add i... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.5.2.2 Decoding process | In the following procedure, steps 1 through 4 describe the computation of the IMDCT, which transforms the N spectral lines into an intermediate single real data block of length 2N using a single N/2 point complex Inverse Fast Fourier Transform (IFFT) with simple pre- and post-phase-shift operations. Steps 5 and 6 descr... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.5.3 Block switching | The following full and partial block lengths can be employed in the AC-4 transform block-switching procedure if the sampling frequency is 44,1 kHz. • 2 048, 1 024, 512, 256, 128 If the sampling frequency is 48 kHz, the following additional block lengths are possible: ETSI ETSI TS 103 190-1 V1.4.1 (2025-07) 189 • 1 920,... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.6 Frame alignment | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.6.1 Introduction | 5. |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 6.1 Introduction | AC-4 is designed to enable artefact-free switching and splicing between different streams, as can happen in adaptive streaming ISO/IEC 23009-1 [1]. When the input of the codec is switched to a different adaptation set, it is important to take into account the codec internal signal and metadata delays. Because some cont... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.6.2 Decoding process | 5. |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 6.2 Decoding process | A decoder shall apply a delay between the input and output PCM samples according to: outn = in − pcm where d_pcm is defined per table 188. Table 188: Delay in frame alignment tool frame_rate PCM signal delay d_pcm [samples] Control data delay d_ctrl [frames] 23,976 288 1 24 288 1 25 352 1 29,97 96 1 30 96 1 47,952... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7 QMF domain processing | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.1 Introduction | AC-4 decoders employ a complex QMF analysis/synthesis filter bank pair to enable alias suppressed frequency-domain processing. The output of the spectral frontend is transformed into a matrix of num_qmf_subbands complex QMF subbands as rows and num_qmf_timeslots time slots as columns, where num_qmf_timeslots is equal t... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.2 QMF control data alignment | The control data of tools operating in QMF domain is at all times aligned with the corresponding spectral frontend data contained in the sf_data element. This means that within a raw AC-4 frame, the control data of any QMF domain tool shall be applied to the spectral data encoded in the very same raw AC-4 frame, regard... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.3 QMF analysis filterbank | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.3.1 Data and control interfaces | A QMF bank is used to split the time domain signal from the core decoder into num_qmf_subbands subband signals. The output from the filterbank, i.e. the subband samples, is complex valued and thus oversampled by a factor two compared to a regular cosine modulated QMF bank. The input of the QMF analysis filterbank are f... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.3.2 Decoding process | The number of QMF subbands in the analysis QMF filter bank, num_qmf_subbands, is always 64. The number of QMF slots is calculated as follows: num_qmf_timeslots = frame_length num_qmf_subbands Table 189 shows the possible values for num_qmf_timeslots. Table 189: Number of QMF time slots frame_length 2 048 1 920 1 536 1 ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.4 QMF synthesis filterbank | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.4.1 Data and control interfaces | Synthesis filtering of the QMF subband signals is achieved using a num_qmf_subbands-subband synthesis QMF bank. The output from the filterbank is real-valued time domain samples. The input to the QMF synthesis filterbank is a set of num_qmf_subbands complex-valued subband signals: • QinQMF,ch Matrix of num_qmf_subbands... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.4.2 Decoding process | The synthesis filtering comprises the following steps, where a vector qsyn_filt consisting of 1 280 samples is assumed: 1) Shift the samples in the vector qsyn_filt by 128 positions. The oldest 128 samples are discarded. 2) The num_qmf_subbands new complex-valued subband samples are multiplied by the matrix N , where: ... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.5 Companding tool | |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.5.1 Data and control interfaces | The companding tool is used to mitigate pre- and post-echo artefacts. It is applied on the Quadrature Mirror Filter domain data. The encoder applies attenuation to signal parts with higher energy and applies gain to signal parts with lower energy. The decoder applies the inverse process, which effectively shapes the co... |
79462c15429e4b02e874d57a1faa88a5 | 103 190-1 | 5.7.5.2 Decoding process | The QMF subband range [sb0, sb1-1] that the companding tool works on shall be determined according to: sb = #acpl_qmf_band in case the codec mode is ASPX_ACPL_1 0 otherwise Sb = aspxxoverbandch The QMF timeslot range [ts0, ts1-1] that the companding tool works on shall be determined according to: ts = atsg_sig[0] × ... |
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