add more informative error info for some common errors

src/flac/encode.c

@@ -1963,7 +1963,7 @@ void print_error_with_state(const EncoderSession *e, const char *message)
 	const int ilen = strlen(e->inbasefilename) + 1;
 	const char *state_string;
 
-	fprintf(stderr, "\n%s: %s\n", e->inbasefilename, message);
+	flac__utils_printf(stderr, 1, "\n%s: %s\n", e->inbasefilename, message);
 
 #ifdef FLAC__HAS_OGG
 	if(e->use_ogg) {
@@ -1984,6 +1984,30 @@ void print_error_with_state(const EncoderSession *e, const char *message)
 	}
 
 	flac__utils_printf(stderr, 1, "%*s state = %s\n", ilen, "", state_string);
+
+	/* print out some more info for some errors: */
+	if (0 == strcmp(state_string, FLAC__StreamEncoderStateString[FLAC__STREAM_ENCODER_NOT_STREAMABLE])) {
+		flac__utils_printf(stderr, 1,
+			"\n"
+			"The encoding parameters specified do not conform to the FLAC Subset and may not\n"
+			"be streamable or playable in hardware devices.  Add --lax to the command-line\n"
+			"options to encode with these parameters.\n"
+		);
+	}
+	else if (0 == strcmp(state_string, FLAC__FileEncoderStateString[FLAC__FILE_ENCODER_FATAL_ERROR_WHILE_WRITING]) || 0 == strcmp(state_string, OggFLAC__FileEncoderStateString[OggFLAC__FILE_ENCODER_FATAL_ERROR_WHILE_WRITING])) {
+		flac__utils_printf(stderr, 1,
+			"\n"
+			"An error occurred while writing; the most common cause is that the disk is full.\n"
+		);
+	}
+	else if (0 == strcmp(state_string, FLAC__FileEncoderStateString[FLAC__FILE_ENCODER_ERROR_OPENING_FILE]) || 0 == strcmp(state_string, OggFLAC__FileEncoderStateString[OggFLAC__FILE_ENCODER_ERROR_OPENING_FILE])) {
+		flac__utils_printf(stderr, 1,
+			"\n"
+			"An error occurred opening the output file; it is likely that the output\n"
+			"directory does not exist or is not writable, the output file already exists and\n"
+			"is not writable, or the disk is full.\n"
+		);
+	}
 }
 
 void print_verify_error(EncoderSession *e)