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Function to generate WAV header for PCM data

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Kovid Goyal 2024-10-10 14:59:56 +05:30
parent 3a273e8766
commit 6a8042f1ed
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GPG Key ID: 06BC317B515ACE7C
1 changed files with 67 additions and 8 deletions
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75
src/calibre/utils/ffmpeg.c
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@ -10,6 +10,7 @@
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <stdbool.h>
#include <libavutil/audio_fifo.h>
#include <libavcodec/avcodec.h>
@ -19,16 +20,19 @@
#include <libavutil/opt.h>
#include <libavutil/mem.h>
#include <libavutil/fifo.h>
#include <libavformat/avformat.h>
#include <libavformat/avio.h>
#include <libswresample/swresample.h>
static PyObject*
averror_as_python(int errnum) {
char buf[4096];
av_strerror(errnum, buf, sizeof(buf));
PyErr_SetString(PyExc_Exception, buf);
averror_as_python(int errnum, int line) {
char avbuf[4096];
av_strerror(errnum, avbuf, sizeof(avbuf));
PyErr_Format(PyExc_Exception, "%s:%d:%s", __FILE__, line, avbuf);
return NULL;
}
// resample_raw_audio_16bit {{{
static PyObject*
resample_raw_audio_16bit(PyObject *self, PyObject *args) {
int input_sample_rate, output_sample_rate, input_num_channels = 1, output_num_channels = 1;
@ -47,9 +51,9 @@ resample_raw_audio_16bit(PyObject *self, PyObject *args) {
&output_layout, fmt, output_sample_rate,
&input_layout, fmt, input_sample_rate,
0, NULL);
if (ret != 0) { av_free(output); PyBuffer_Release(&inb); return averror_as_python(ret); }
if (ret != 0) { av_free(output); PyBuffer_Release(&inb); return averror_as_python(ret, __LINE__); }
#define free_resources av_free(output); PyBuffer_Release(&inb); swr_free(&swr_ctx);
if ((ret = swr_init(swr_ctx)) < 0) { free_resources; return averror_as_python(ret); }
if ((ret = swr_init(swr_ctx)) < 0) { free_resources; return averror_as_python(ret, __LINE__); }
const uint8_t *input = inb.buf;
Py_BEGIN_ALLOW_THREADS
ret = swr_convert(swr_ctx,
@ -57,14 +61,66 @@ resample_raw_audio_16bit(PyObject *self, PyObject *args) {
&input, inb.len / (input_num_channels * bytes_per_sample)
);
Py_END_ALLOW_THREADS
if (ret < 0) { free_resources; return averror_as_python(ret); }
if (ret < 0) { free_resources; return averror_as_python(ret, __LINE__); }
output_size = ret * output_num_channels * bytes_per_sample;
PyObject *ans = PyBytes_FromStringAndSize((char*)output, output_size);
free_resources;
#undef free_resources
return ans;
}
} // }}}
// wav_header_for_pcm_data {{{
static PyObject*
wav_header_for_pcm_data(PyObject *self, PyObject *args) {
unsigned int sample_rate = 22050, num_channels=1, audio_data_size=0;
if (!PyArg_ParseTuple(args, "|III", &audio_data_size, &sample_rate, &num_channels)) return NULL;
struct {
char riff[4];
uint32_t file_size;
char wave[4];
char fmt[4];
uint32_t block_size;
uint16_t audio_format;
uint16_t num_channels;
uint32_t sample_rate;
uint32_t byte_rate;
uint16_t bytes_per_block;
uint16_t bits_per_sample;
char data[4];
uint32_t subchunk2_size;
} wav_header;
wav_header.riff[0] = 'R';
wav_header.riff[1] = 'I';
wav_header.riff[2] = 'F';
wav_header.riff[3] = 'F';
wav_header.wave[0] = 'W';
wav_header.wave[1] = 'A';
wav_header.wave[2] = 'V';
wav_header.wave[3] = 'E';
wav_header.fmt[0] = 'f';
wav_header.fmt[1] = 'm';
wav_header.fmt[2] = 't';
wav_header.fmt[3] = ' ';
wav_header.data[0] = 'd';
wav_header.data[1] = 'a';
wav_header.data[2] = 't';
wav_header.data[3] = 'a';
wav_header.file_size = audio_data_size + sizeof(wav_header) - 8;
wav_header.bits_per_sample = 16; // number of bits per sample per channel
wav_header.block_size = wav_header.bits_per_sample;
wav_header.audio_format = 1; // 1 for PCM 3 for float32
wav_header.num_channels = num_channels; // Mono
wav_header.sample_rate = sample_rate;
wav_header.bytes_per_block = num_channels * wav_header.bits_per_sample / 8;
wav_header.byte_rate = sample_rate * wav_header.bytes_per_block;
wav_header.subchunk2_size = audio_data_size;
return PyBytes_FromStringAndSize((void*)&wav_header, sizeof(wav_header));
}
// }}}
// Boilerplate {{{
static int
@ -76,6 +132,9 @@ CALIBRE_MODINIT_FUNC PyInit_ffmpeg(void) {
{"resample_raw_audio_16bit", (PyCFunction)resample_raw_audio_16bit, METH_VARARGS,
"resample_raw_audio(input_data, input_sample_rate, output_sample_rate, input_num_channels=1, output_num_channels=1) -> Return resampled raw audio data."
},
{"wav_header_for_pcm_data", (PyCFunction)wav_header_for_pcm_data, METH_VARARGS,
"wav_header_for_pcm_data(audio_data_size=0, sample_rate=22050, num_channels=1) -> WAV header for specified amount of PCM data as bytestring"
},
{0} /* Sentinel */
};
static struct PyModuleDef module_def = {