Add example code to exercise mpg123_framedata: An MPEG stream cleaner (just extracting all valid frames).

Also updating the examples Makefile a bit.


git-svn-id: svn://scm.orgis.org/mpg123/trunk@2911 35dc7657-300d-0410-a2e5-dc2837fedb53

doc/examples/extract_frames.c

@@ -0,0 +1,92 @@
+/*
+	extract_frams: utlize the framebyframe API and mpg123_framedata to extract the MPEG frames out of a stream (strip off anything else).
+
+	copyright 2011 by the mpg123 project - free software under the terms of the LGPL 2.1
+	see COPYING and AUTHORS files in distribution or http://mpg123.org
+	initially written by Thomas Orgis
+*/
+
+#include <mpg123.h>
+
+/* unistd.h is not available under MSVC, 
+ io.h defines the read and write functions */
+#ifndef _MSC_VER
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+
+#include <stdio.h>
+
+int do_work(mpg123_handle *m);
+
+int main(int argc, char **argv)
+{
+	int ret = 0;
+	mpg123_handle *m;
+
+	mpg123_init();
+	m = mpg123_new(NULL, &ret);
+
+	if(m == NULL)
+	{
+		fprintf(stderr, "Cannot create handle: %s", mpg123_plain_strerror(ret));
+	}
+	else
+	{
+		fprintf(stderr, "I'll take your dirty MPEG audio from standard input and will write the extrated pure MPEG data to stadard output.\n");
+		if(argc > 1 && strcmp(argv[1], "--noinfo") == 0)
+		{
+			fprintf(stderr, "Enabling parsing/consuming of the Info frame so that it will not appear in output.\n");
+			ret = mpg123_param(m, MPG123_REMOVE_FLAGS, MPG123_IGNORE_INFOFRAME, 0.);
+		}
+		else
+		{
+			fprintf(stderr, "If you'd have given --noinfo as argument, I would omit a LAME/Xing info frame.\n");
+			ret = mpg123_param(m, MPG123_ADD_FLAGS, MPG123_IGNORE_INFOFRAME, 0.);
+		}
+		if(ret == 0) ret = do_work(m);
+
+		if(ret != 0) fprintf(stderr, "Some error occured: %s\n", mpg123_strerror(m));
+
+
+		mpg123_delete(m); /* Closes, too. */
+	}
+	mpg123_exit();
+
+	return ret;
+}
+
+int do_work(mpg123_handle *m)
+{
+	int ret;
+	size_t count = 0;
+	ret = mpg123_open_fd(m, STDIN_FILENO);
+	if(ret != MPG123_OK) return ret;
+
+	while( (ret = mpg123_framebyframe_next(m)) == MPG123_OK || ret == MPG123_NEW_FORMAT )
+	{
+		unsigned long header;
+		unsigned char *bodydata;
+		size_t bodybytes;
+		if(mpg123_framedata(m, &header, &bodydata, &bodybytes) == MPG123_OK)
+		{
+			/* Need to extract the 4 header bytes from the native storage in the correct order. */
+			unsigned char hbuf[4];
+			int i;
+			for(i=0; i<4; ++i) hbuf[i] = (unsigned char) ((header >> ((3-i)*8)) & 0xff);
+
+			/* Now write out both header and data, fire and forget. */
+			write(STDOUT_FILENO, hbuf, 4);
+			write(STDOUT_FILENO, bodydata, bodybytes);
+			fprintf(stderr, "%zu: header 0x%08x, %zu body bytes\n", ++count, header, bodybytes);
+		}
+	}
+
+	if(ret != MPG123_DONE)
+	fprintf(stderr, "Some error occured (non-fatal?): %s\n", mpg123_strerror(m));
+
+	fprintf(stderr, "Done with %zu MPEG frames.\n", count);
+
+	return 0;
+}