[Libav-user] Converting audio sample format from s32le to f32le using libswresample/av_convert

Haridas Sagar N haridassagarn at tataelxsi.co.in
Sun Feb 24 14:39:25 CET 2013

Hello Everyone,

I am new to ffmpeg and I am working on AAC encoder, I tried encoding the pcm sample having f32le sample format but whatever the pcm sample format i am having is  s32le so i need to convert it to f32le,I tried with ffmpeg's resampling_audio.c example and i have modified the code to take pcm file as input.. but the output file size is always ~=11000 bytes and it is not playing

Also i tried with very the following code but swr_convert() is returning -22 and i am not sure what ever code i got/written is correct...

Here is the sample code i am trying currently

int main(int argc, char **argv)
uint8_t *dst,*dstp;
uint8_t *outbuf;
int ret;
size_t bufsize;
FILE *fout=NULL;
struct SwrContext *ctx = NULL;
char *filename=argv[1];
fp = fopen("FLTP1.pcm","rb");
fout = fopen(filename,"wb");

if (fseek(fp, 0L, SEEK_END) == 0)

fseek(fp, 0L, SEEK_SET);

printf(" buf size is %d\n",bufsize);
dstp=( uint8_t *)malloc(sizeof(uint8_t) * (bufsize + 1));
outbuf=( uint8_t *)malloc(sizeof(uint32_t) * (bufsize*1000 + 1));
printf(" reading samples from file\n");
printf(" return value is %d\n",ret);

ctx = swr_alloc_set_opts(ctx,AV_CH_LAYOUT_STEREO,AV_SAMPLE_FMT_S32,48000,
if(swr_init(ctx) < 0)
     return -1;

printf(" converting\n");

int  resample_samples = swr_convert(ctx,(uint8_t**)&outbuf,bufsize*1000,
                                         (const uint8_t**)&dst,bufsize);
printf(" return value is %d\n",resample_samples);
printf(" writing to file\n");


printf(" wrote to file\n");



return 0;


It will be of great help to me  if you provide me with any suggestions/help

Thanks in advance

Best regards

Haridas Sagar N

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