[Freeswitch-dev] Transcoding a sound bite.

14 Feb 2014

      I’m trying to write a function that will open a sound file in PCMU format and transcode it to G722. My function is based on the fs_encoder.c file from FreeSWITCH itself. It works, sort of. It does successfully create a playable G722 file, but it plays back at 2X the speed as the PCMU and sounds like Alvin & the Chipmunks. The G722 file is also about half the size of the PCMU but I expected them to be about the same. Other snippets we have in both PCMU and G722, that play correctly, are about the same.

I’ve tried changing the rates around in but nothing seems to work.

Below is the code, anyone see my bug?

Thanks in advance,
Kevin

#include <switch.h>
#include <switch_version.h>

void fs_encode(int argc, char** argv, switch_stream_handle_t* stream)
{
    switch_status_t status;
switch_memory_pool_t*   pool = NULL;
switch_file_handle_t fh_input = { 0 };
    switch_file_handle_t fh_output = { 0 };
int channels = 1;
uint32_t rate = 8000;
int ptime = 20;
int bitrate = 0;
const char* input = "/etc/freeswitch/conf/sounds/three.PCMU";
const char* inFormat = "PCMU";
const char* output = "/out.G722";
const char* outFormat = "G722";
switch_codec_t inCodec = { 0 };
switch_codec_t outCodec = { 0 };
const char* fmtp = "";

int blocksize = 0;

char readBuf[2048];
switch_size_t len = sizeof(readBuf)/2;

    char decode_buf[2048];
    uint32_t decoded_len = 0;
uint32_t decoded_rate = 0;

    char encode_buf[2048];
    uint32_t encoded_len = 0;
uint32_t encoded_rate = 0;
    unsigned int flags = 0;

switch_core_new_memory_pool(&pool);

stream->write_function(stream, "Opening input file %s\n", input);
    status = switch_core_file_open(&fh_input, input, channels, rate, SWITCH_FILE_FLAG_READ | SWITCH_FILE_DATA_SHORT, NULL);
    if( status != SWITCH_STATUS_SUCCESS )
    {
stream->write_function(stream, "Couldn't open input file %s.  Status = %d\n", input, status);
goto end;
}

stream->write_function(stream, "Opening output file %s\n", output);
status = switch_core_file_open(&fh_output, output, channels, rate, SWITCH_FILE_FLAG_WRITE | SWITCH_FILE_NATIVE, NULL);
    if( status != SWITCH_STATUS_SUCCESS )
    {
stream->write_function(stream, "Couldn't open output file %s.  Status = %d\n", output, status);
goto end;
}

    stream->write_function(stream, "Opening a %s codec\n", inFormat);
status = switch_core_codec_init_with_bitrate(&inCodec, inFormat, fmtp, rate, ptime, channels, bitrate, SWITCH_CODEC_FLAG_DECODE, NULL, pool);
    if( status != SWITCH_STATUS_SUCCESS )
    {
stream->write_function(stream, "Couldn't initialize codec for %s@%dh@%di\n", inFormat, rate, ptime);
goto end;
}

    stream->write_function(stream, "Opening a %s codec\n", outFormat);
status = switch_core_codec_init_with_bitrate(&outCodec, outFormat, fmtp, rate, ptime, channels, bitrate, SWITCH_CODEC_FLAG_ENCODE, NULL, pool);
    if( status != SWITCH_STATUS_SUCCESS )
    {
stream->write_function(stream, "Couldn't initialize codec for %s@%dh@%di\n", outFormat, rate, ptime);
goto end;
}

blocksize = len = (rate*ptime)/1000;
switch_assert(sizeof(readBuf) >= len * 2);
stream->write_function(stream, "Frame size is %d\n", blocksize);
    do
    {
        stream->write_function(stream, "loop\n");

            /////////////////////////////////////////////////////////////////////////////////////
            // Read input data
        len = blocksize;
        stream->write_function(stream, "Attempt to read %d bytes from %s\n",len,input);
        status = switch_core_file_read(&fh_input, readBuf, &len);
        if( status != SWITCH_STATUS_SUCCESS )
        {
            stream->write_function(stream, "Read error %d\n",status);
            goto end;
        }
        stream->write_function(stream, "Read %d bytes from %s\n",len,input);

            /////////////////////////////////////////////////////////////////////////////////////
            // Decode data
        stream->write_function(stream, "Attempt to decode %d bytes\n",len);
        decoded_len = sizeof(decode_buf);
        decoded_rate = rate;
        status = switch_core_codec_decode(&inCodec, NULL, readBuf, len, rate, decode_buf, &decoded_len, &decoded_rate, &flags);
        if( status != SWITCH_STATUS_SUCCESS )
        {
            stream->write_function(stream, "Codec decode error %d\n",status);
            goto end;
        }
        stream->write_function(stream, "Decoded %d bytes with %d rate\n",decoded_len,decoded_rate);

            /////////////////////////////////////////////////////////////////////////////////////
            // Encode data
        stream->write_function(stream, "Attempt to encode %d bytes\n",decoded_len);
        encoded_len = sizeof(encode_buf);
        status = switch_core_codec_encode(&outCodec, NULL, decode_buf, decoded_len, decoded_rate, encode_buf, &encoded_len, &encoded_rate, &flags);
        if( status != SWITCH_STATUS_SUCCESS )
        {
            stream->write_function(stream, "Codec encode error %d\n",status);
            goto end;
        }
        stream->write_function(stream, "Encoded %d bytes with %d rate\n",encoded_len,encoded_rate);

        len = encoded_len;

            /////////////////////////////////////////////////////////////////////////////////////
            // Write data
        stream->write_function(stream, "Write %d bytes\n",encoded_len);
        status = switch_core_file_write(&fh_output, encode_buf, &encoded_len);
        if( status != SWITCH_STATUS_SUCCESS )
        {
            stream->write_function(stream, "Write error %d\n",status);
            goto end;
        }

    } while(1);

end:
    if( fh_input.file_interface )
    {
switch_core_file_close(&fh_input);
}
if( fh_output.file_interface )
    {
switch_core_file_close(&fh_output);
}

    switch_core_codec_destroy(&outCodec);
    switch_core_codec_destroy(&inCodec);

if( pool )
    {
switch_core_destroy_memory_pool(&pool);
}
}

[Freeswitch-dev] Transcoding a sound bite.

Kevin Snow