Vorbisfile documentation |
Chris@1: vorbisfile version 1.3.2 - 20101101 |
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Chris@1: The following is a run-through of the chaining example program supplied Chris@1: with vorbisfile - chaining_example.c. Chris@1: This program demonstrates how to work with a chained bitstream. Chris@1: Chris@1:
Chris@1: First, relevant headers, including vorbis-specific "codec.h" and "vorbisfile.h" have to be included.
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Chris@1: Chris@1: #include "vorbis/codec.h" Chris@1: #include "vorbis/vorbisfile.h" Chris@1: #include "../lib/misc.h" Chris@1:Chris@1: |
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Inside main(), we declare our primary OggVorbis_File structure. We also declare a other helpful variables to track our progress within the file.
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Chris@1: int main(){
Chris@1: OggVorbis_File ov;
Chris@1: int i;
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This example takes its input on stdin which is in 'text' mode by default under Windows; this will corrupt the input data unless set to binary mode. This applies only to Windows.
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Chris@1: Chris@1: #ifdef _WIN32 /* We need to set stdin to binary mode under Windows */ Chris@1: _setmode( _fileno( stdin ), _O_BINARY ); Chris@1: #endif Chris@1:Chris@1: |
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We call ov_open_callbacks() to Chris@1: initialize the OggVorbis_File Chris@1: structure. ov_open_callbacks() Chris@1: also checks to ensure that we're reading Vorbis format and not Chris@1: something else. The OV_CALLBACKS_NOCLOSE callbacks instruct Chris@1: libvorbisfile not to close stdin later during cleanup.
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Chris@1: if(ov_open_callbacks(stdin,&ov,NULL,-1,OV_CALLBACKS_NOCLOSE)<0){
Chris@1: printf("Could not open input as an OggVorbis file.\n\n");
Chris@1: exit(1);
Chris@1: }
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Chris@1: First we check to make sure the stream is seekable using ov_seekable. Chris@1: Chris@1:
Then we're going to find the number of logical bitstreams in the physical bitstream using ov_streams. Chris@1: Chris@1:
We use ov_time_total to determine the total length of the physical bitstream. We specify that we want the entire bitstream by using the argument -1.
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Chris@1: if(ov_seekable(&ov)){
Chris@1: printf("Input bitstream contained %ld logical bitstream section(s).\n",
Chris@1: ov_streams(&ov));
Chris@1: printf("Total bitstream playing time: %ld seconds\n\n",
Chris@1: (long)ov_time_total(&ov,-1));
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Chris@1: }else{
Chris@1: printf("Standard input was not seekable.\n"
Chris@1: "First logical bitstream information:\n\n");
Chris@1: }
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Now we're going to iterate through each logical bitstream and print information about that bitstream. Chris@1: Chris@1:
We use ov_info to pull out the vorbis_info struct for each logical bitstream. This struct contains bitstream-specific info. Chris@1: Chris@1:
ov_serialnumber retrieves the unique serial number for the logical bistream. ov_raw_total gives the total compressed bytes for the logical bitstream, and ov_time_total gives the total time in the logical bitstream.
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Chris@1: for(i=0;i<ov_streams(&ov);i++){
Chris@1: vorbis_info *vi=ov_info(&ov,i);
Chris@1: printf("\tlogical bitstream section %d information:\n",i+1);
Chris@1: printf("\t\t%ldHz %d channels bitrate %ldkbps serial number=%ld\n",
Chris@1: vi->rate,vi->channels,ov_bitrate(&ov,i)/1000,
Chris@1: ov_serialnumber(&ov,i));
Chris@1: printf("\t\tcompressed length: %ld bytes ",(long)(ov_raw_total(&ov,i)));
Chris@1: printf(" play time: %lds\n",(long)ov_time_total(&ov,i));
Chris@1: }
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Chris@1: When we're done with the entire physical bitstream, we need to call ov_clear() to release the bitstream.
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Chris@1: Chris@1: ov_clear(&ov); Chris@1: return 0; Chris@1: } Chris@1:Chris@1: |
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Chris@1: The full source for chaining_example.c can be found with the vorbis
Chris@1: distribution in chaining_example.c.
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copyright © 2000-2010 Xiph.Org |
Chris@1: Chris@1: |
Vorbisfile documentation |
Chris@1: vorbisfile version 1.3.2 - 20101101 |
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