The Intel/DVI ADPCM algorithm hasīeen selected for use by the IMA, so it may well become a standard. ADPCM coding is an adaptiveĬoding scheme, whereby each 4 bit number is the difference between one sampleĪnd the next, divided by a (varying) step. lin2adpcm ( fragment, width, state ) ¶Ĭonvert samples to 4 bit Intel/DVI ADPCM encoding. Return the value of sample index from the fragment. The routine takes time proportional to len(fragment). The fragments should both contain 2-byte samples. Maximum energy, i.e., return i for which rms(fragment)
Search fragment for a slice of length length samples (not bytes!) with Return a tuple (offset, factor) where offset is the (integer) offset intoįragment where the optimal match started and factor is the (floating-point)įactor as per findfactor(). Out of fragment, using findfactor() to compute the best match, and This is (conceptually) done by taking slices Try to match reference as well as possible to a portion of fragment (which The time taken by this routine is proportional to len(fragment). Make it match as well as possible to fragment. Minimal, i.e., return the factor with which you should multiply reference to Return a factor F such that rms(add(fragment, mul(reference, -F))) is Return the number of zero crossings in the fragment passed as an argument. “Byteswap” all samples in a fragment and returns the modified fragment.Ĭonverts big-endian samples to little-endian and vice versa. Return a fragment that is the original fragment with a bias added to each Noįiltering is done, so the usefulness of this routine is questionable. Return the average peak-peak value over all samples in the fragment. Return the average over all samples in the fragment. alaw2lin ( fragment, width ) ¶Ĭonvert sound fragments in a-LAW encoding to linearly encoded sound fragments.Ī-LAW encoding always uses 8 bits samples, so width refers only to the sample (sample, newstate) where the sample has the width specified in width. See theĭescription of lin2adpcm() for details on ADPCM coding. adpcm2lin ( adpcmfragment, width, state ) ¶ĭecode an Intel/DVI ADPCM coded fragment to a linear fragment. Samples are truncated in case of overflow. Bothįragments should have the same length. Width is the sample width in bytes, either 1, 2, 3 or 4. Return a fragment which is the addition of the two samples passed as parameters. This exception is raised on all errors, such as unknown number of bytes per The module defines the following variables and functions: exception audioop. Sample size (in bytes) is always a parameter of the operation. This module provides support for a-LAW, u-LAW and Intel/DVI ADPCM encodings.Ī few of the more complicated operations only take 16-bit samples, otherwise the String input now results in an immediate error. & msg.Changed in version 3.4: Support for 24-bit samples was added.Īll functions now accept any bytes-like object. If (msg.source_type = AUDIO_ELEMENT_TYPE_ELEMENT & msg.source = (void *) mp3_decoder Mp3_decoder = mp3_decoder_init(&mp3_cfg) Īudio_element_set_read_cb(mp3_decoder, my_read_cb, NULL) ĮSP_LOGE(TAG, " Register all elements to audio pipeline") Īudio_pipeline_register(pipeline, mp3_decoder, "mp3") Īudio_pipeline_register(pipeline, i2s_stream_writer, "i2s") Īudio_pipeline_link(pipeline, (const char *), 2) ĮSP_LOGE(TAG, " Set up event listener") Īudio_event_iface_cfg_t evt_cfg = AUDIO_EVENT_IFACE_DEFAULT_CFG() Īudio_event_iface_handle_t evt = audio_event_iface_init(&evt_cfg) ĮSP_LOGE(TAG, " Listening event from all elements of pipeline") Īudio_pipeline_set_listener(pipeline, evt) ĮSP_LOGE(TAG, " Start audio_pipeline") Įsp_err_t ret = audio_event_iface_listen(evt, &msg, portMAX_DELAY) ĮSP_LOGE(TAG, " Event interface error : %d", ret) Mp3_decoder_cfg_t mp3_cfg = DEFAULT_MP3_DECODER_CONFIG() I2s_stream_writer = i2s_stream_init(&i2s_cfg) ĮSP_LOGE(TAG, " Create mp3 decoder to decode mp3 data") I2s_stream_cfg_t i2s_cfg = I2S_STREAM_CFG_UDA1334A() // I2S_STREAM_CFG_DEFAULT() Pipeline = audio_pipeline_init(&pipeline_cfg) ĮSP_LOGE(TAG, " Create i2s stream to write data to codec chip") Static void play_task(void *pvParameters)Īudio_element_handle_t i2s_stream_writer, mp3_decoder ĮSP_LOGE(TAG, " Create audio pipeline, add all elements to pipeline, and subscribe pipeline event") Īudio_pipeline_cfg_t pipeline_cfg = DEFAULT_AUDIO_PIPELINE_CONFIG() Static int my_read_cb(audio_element_handle_t el, char *buf, int len, TickType_t wait_time, void *ctx)ĮSP_LOGE(TAG, "REACHED END OF MP3 FILE")