circuitpython/shared-module/audiomp3/MP3Decoder.c

/*
 * This file is part of the Micro Python project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Scott Shawcroft for Adafruit Industries
 * Copyright (c) 2019 Jeff Epler for Adafruit Industries
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "shared-bindings/audiomp3/MP3Decoder.h"

#include <stdint.h>
#include <string.h>
#include <math.h>

#include "py/mperrno.h"
#include "py/runtime.h"

#include "shared-module/audiomp3/MP3Decoder.h"
#include "supervisor/shared/translate.h"
#include "supervisor/background_callback.h"
#include "lib/mp3/src/mp3common.h"

#define MAX_BUFFER_LEN (MAX_NSAMP * MAX_NGRAN * MAX_NCHAN * sizeof(int16_t))

/** Fill the input buffer unconditionally.
 *
 * Returns true if the input buffer contains any useful data,
 * false otherwise.  (The input buffer will be padded to the end with
 * 0 bytes, which do not interfere with MP3 decoding)
 *
 * Raises OSError if f_read fails.
 *
 * Sets self->eof if any read of the file returns 0 bytes
 */
STATIC bool mp3file_update_inbuf_always(audiomp3_mp3file_obj_t *self) {
    // If we didn't previously reach the end of file, we can try reading now
    if (!self->eof) {

        // Move the unconsumed portion of the buffer to the start
        uint8_t *end_of_buffer = self->inbuf + self->inbuf_length;
        uint8_t *new_end_of_data = self->inbuf + self->inbuf_length - self->inbuf_offset;
        memmove(self->inbuf, self->inbuf + self->inbuf_offset,
            self->inbuf_length - self->inbuf_offset);
        self->inbuf_offset = 0;

        UINT to_read = end_of_buffer - new_end_of_data;
        UINT bytes_read = 0;
        memset(new_end_of_data, 0, to_read);
        if (f_read(&self->file->fp, new_end_of_data, to_read, &bytes_read) != FR_OK) {
            self->eof = true;
            mp_raise_OSError(MP_EIO);
        }

        if (bytes_read == 0) {
            self->eof = true;
        }

        if (to_read != bytes_read) {
            new_end_of_data += bytes_read;
            memset(new_end_of_data, 0, end_of_buffer - new_end_of_data);
        }

    }

    // Return true iff there are at least some useful bytes in the buffer
    return self->inbuf_offset < self->inbuf_length;
}

/** Update the inbuf from a background callback.
 *
 * This variant is introduced so that at the site of the
 * add_background_callback_core call, the prototype matches.
 */
STATIC void mp3file_update_inbuf_cb(void *self) {
    mp3file_update_inbuf_always(self);
}

/** Fill the input buffer if it is less than half full.
 *
 * Returns the same as mp3file_update_inbuf_always.
 */
STATIC bool mp3file_update_inbuf_half(audiomp3_mp3file_obj_t *self) {
    // If buffer is over half full, do nothing
    if (self->inbuf_offset < self->inbuf_length / 2) {
        return true;
    }

    return mp3file_update_inbuf_always(self);
}

#define READ_PTR(self) (self->inbuf + self->inbuf_offset)
#define BYTES_LEFT(self) (self->inbuf_length - self->inbuf_offset)
#define CONSUME(self, n) (self->inbuf_offset += n)

// http://id3.org/d3v2.3.0
// http://id3.org/id3v2.3.0
STATIC void mp3file_skip_id3v2(audiomp3_mp3file_obj_t *self) {
    mp3file_update_inbuf_half(self);
    if (BYTES_LEFT(self) < 10) {
        return;
    }
    uint8_t *data = READ_PTR(self);
    if (!(
        data[0] == 'I' &&
        data[1] == 'D' &&
        data[2] == '3' &&
        data[3] != 0xff &&
        data[4] != 0xff &&
        (data[5] & 0x1f) == 0 &&
        (data[6] & 0x80) == 0 &&
        (data[7] & 0x80) == 0 &&
        (data[8] & 0x80) == 0 &&
        (data[9] & 0x80) == 0)) {
        return;
    }
    uint32_t size = (data[6] << 21) | (data[7] << 14) | (data[8] << 7) | (data[9]);
    size += 10; // size excludes the "header" (but not the "extended header")
    // First, deduct from size whatever is left in buffer
    uint32_t to_consume = MIN(size, BYTES_LEFT(self));
    CONSUME(self, to_consume);
    size -= to_consume;

    // Next, seek in the file after the header
    f_lseek(&self->file->fp, f_tell(&self->file->fp) + size);
    return;
}

/* If a sync word can be found, advance to it and return true.  Otherwise,
 * return false.
 */
STATIC bool mp3file_find_sync_word(audiomp3_mp3file_obj_t *self) {
    do {
        mp3file_update_inbuf_half(self);
        int offset = MP3FindSyncWord(READ_PTR(self), BYTES_LEFT(self));
        if (offset >= 0) {
            CONSUME(self, offset);
            mp3file_update_inbuf_half(self);
            return true;
        }
        CONSUME(self, MAX(0, BYTES_LEFT(self) - 16));
    } while (!self->eof);
    return false;
}

STATIC bool mp3file_get_next_frame_info(audiomp3_mp3file_obj_t *self, MP3FrameInfo *fi) {
    int err;
    do {
        err = MP3GetNextFrameInfo(self->decoder, fi, READ_PTR(self));
        if (err == ERR_MP3_NONE) {
            break;
        }
        CONSUME(self, 1);
        mp3file_find_sync_word(self);
    } while (!self->eof);
    return err == ERR_MP3_NONE;
}

void common_hal_audiomp3_mp3file_construct(audiomp3_mp3file_obj_t *self,
    pyb_file_obj_t *file,
    uint8_t *buffer,
    size_t buffer_size) {
    // XXX Adafruit_MP3 uses a 2kB input buffer and two 4kB output buffers.
    // for a whopping total of 10kB buffers (+mp3 decoder state and frame buffer)
    // At 44kHz, that's 23ms of output audio data.
    //
    // We will choose a slightly different allocation strategy for the output:
    // Make sure the buffers are sized exactly to match (a multiple of) the
    // frame size; this is typically 2304 * 2 bytes, so a little bit bigger
    // than the two 4kB output buffers, except that the alignment allows to
    // never allocate that extra frame buffer.

    self->inbuf_length = 2048;
    self->inbuf_offset = self->inbuf_length;
    self->inbuf = m_malloc(self->inbuf_length, false);
    if (self->inbuf == NULL) {
        common_hal_audiomp3_mp3file_deinit(self);
        mp_raise_msg(&mp_type_MemoryError,
            translate("Couldn't allocate input buffer"));
    }
    self->decoder = MP3InitDecoder();
    if (self->decoder == NULL) {
        common_hal_audiomp3_mp3file_deinit(self);
        mp_raise_msg(&mp_type_MemoryError,
            translate("Couldn't allocate decoder"));
    }

    if ((intptr_t)buffer & 1) {
        buffer += 1;
        buffer_size -= 1;
    }
    if (buffer_size >= 2 * MAX_BUFFER_LEN) {
        self->buffers[0] = (int16_t *)(void *)buffer;
        self->buffers[1] = (int16_t *)(void *)(buffer + MAX_BUFFER_LEN);
    } else {
        self->buffers[0] = m_malloc(MAX_BUFFER_LEN, false);
        if (self->buffers[0] == NULL) {
            common_hal_audiomp3_mp3file_deinit(self);
            mp_raise_msg(&mp_type_MemoryError,
                translate("Couldn't allocate first buffer"));
        }

        self->buffers[1] = m_malloc(MAX_BUFFER_LEN, false);
        if (self->buffers[1] == NULL) {
            common_hal_audiomp3_mp3file_deinit(self);
            mp_raise_msg(&mp_type_MemoryError,
                translate("Couldn't allocate second buffer"));
        }
    }

    common_hal_audiomp3_mp3file_set_file(self, file);
}

void common_hal_audiomp3_mp3file_set_file(audiomp3_mp3file_obj_t *self, pyb_file_obj_t *file) {
    background_callback_begin_critical_section();

    self->file = file;
    f_lseek(&self->file->fp, 0);
    self->inbuf_offset = self->inbuf_length;
    self->eof = 0;
    self->other_channel = -1;
    mp3file_update_inbuf_half(self);
    mp3file_find_sync_word(self);
    // It **SHOULD** not be necessary to do this; the buffer should be filled
    // with fresh content before it is returned by get_buffer().  The fact that
    // this is necessary to avoid a glitch at the start of playback of a second
    // track using the same decoder object means there's still a bug in
    // get_buffer() that I didn't understand.
    memset(self->buffers[0], 0, MAX_BUFFER_LEN);
    memset(self->buffers[1], 0, MAX_BUFFER_LEN);
    MP3FrameInfo fi;
    bool result = mp3file_get_next_frame_info(self, &fi);
    background_callback_end_critical_section();
    if (!result) {
        mp_raise_msg(&mp_type_RuntimeError,
            translate("Failed to parse MP3 file"));
    }

    self->sample_rate = fi.samprate;
    self->channel_count = fi.nChans;
    self->frame_buffer_size = fi.outputSamps * sizeof(int16_t);
    self->len = 2 * self->frame_buffer_size;
}

void common_hal_audiomp3_mp3file_deinit(audiomp3_mp3file_obj_t *self) {
    MP3FreeDecoder(self->decoder);
    self->decoder = NULL;
    self->inbuf = NULL;
    self->buffers[0] = NULL;
    self->buffers[1] = NULL;
    self->file = NULL;
}

bool common_hal_audiomp3_mp3file_deinited(audiomp3_mp3file_obj_t *self) {
    return self->buffers[0] == NULL;
}

uint32_t common_hal_audiomp3_mp3file_get_sample_rate(audiomp3_mp3file_obj_t *self) {
    return self->sample_rate;
}

void common_hal_audiomp3_mp3file_set_sample_rate(audiomp3_mp3file_obj_t *self,
    uint32_t sample_rate) {
    self->sample_rate = sample_rate;
}

uint8_t common_hal_audiomp3_mp3file_get_bits_per_sample(audiomp3_mp3file_obj_t *self) {
    return 16;
}

uint8_t common_hal_audiomp3_mp3file_get_channel_count(audiomp3_mp3file_obj_t *self) {
    return self->channel_count;
}

void audiomp3_mp3file_reset_buffer(audiomp3_mp3file_obj_t *self,
    bool single_channel_output,
    uint8_t channel) {
    if (single_channel_output && channel == 1) {
        return;
    }
    // We don't reset the buffer index in case we're looping and we have an odd number of buffer
    // loads
    background_callback_begin_critical_section();
    f_lseek(&self->file->fp, 0);
    self->inbuf_offset = self->inbuf_length;
    self->eof = 0;
    self->other_channel = -1;
    mp3file_update_inbuf_half(self);
    mp3file_skip_id3v2(self);
    mp3file_find_sync_word(self);
    background_callback_end_critical_section();
}

audioio_get_buffer_result_t audiomp3_mp3file_get_buffer(audiomp3_mp3file_obj_t *self,
    bool single_channel_output,
    uint8_t channel,
    uint8_t **bufptr,
    uint32_t *buffer_length) {
    if (!self->inbuf) {
        *buffer_length = 0;
        return GET_BUFFER_ERROR;
    }
    if (!single_channel_output) {
        channel = 0;
    }

    *buffer_length = self->frame_buffer_size;

    if (channel == self->other_channel) {
        *bufptr = (uint8_t *)(self->buffers[self->other_buffer_index] + channel);
        self->other_channel = -1;
        return GET_BUFFER_MORE_DATA;
    }


    self->buffer_index = !self->buffer_index;
    self->other_channel = 1 - channel;
    self->other_buffer_index = self->buffer_index;
    int16_t *buffer = (int16_t *)(void *)self->buffers[self->buffer_index];
    *bufptr = (uint8_t *)buffer;

    mp3file_skip_id3v2(self);
    if (!mp3file_find_sync_word(self)) {
        *buffer_length = 0;
        return self->eof ? GET_BUFFER_DONE : GET_BUFFER_ERROR;
    }
    int bytes_left = BYTES_LEFT(self);
    uint8_t *inbuf = READ_PTR(self);
    int err = MP3Decode(self->decoder, &inbuf, &bytes_left, buffer, 0);
    CONSUME(self, BYTES_LEFT(self) - bytes_left);

    if (err) {
        *buffer_length = 0;
        return GET_BUFFER_DONE;
    }

    if (self->inbuf_offset >= 512) {
        background_callback_add(
            &self->inbuf_fill_cb,
            mp3file_update_inbuf_cb,
            self);
    }

    return GET_BUFFER_MORE_DATA;
}

void audiomp3_mp3file_get_buffer_structure(audiomp3_mp3file_obj_t *self, bool single_channel_output,
    bool *single_buffer, bool *samples_signed,
    uint32_t *max_buffer_length, uint8_t *spacing) {
    *single_buffer = false;
    *samples_signed = true;
    *max_buffer_length = self->frame_buffer_size;
    if (single_channel_output) {
        *spacing = self->channel_count;
    } else {
        *spacing = 1;
    }
}

float common_hal_audiomp3_mp3file_get_rms_level(audiomp3_mp3file_obj_t *self) {
    float sumsq = 0.f;
    // Assumes no DC component to the audio.  Is that a safe assumption?
    int16_t *buffer = (int16_t *)(void *)self->buffers[self->buffer_index];
    for (size_t i = 0; i < self->frame_buffer_size / sizeof(int16_t); i++) {
        sumsq += (float)buffer[i] * buffer[i];
    }
    return sqrtf(sumsq) / (self->frame_buffer_size / sizeof(int16_t));
}