Improve foreign metadata handling

Add options --keep-foreign-metadata-if-present and improve error
messages when on decoding the wrong type of foreign metadata is
found.

10 files changed, 132 insertions, 38 deletions

diff --git a/man/flac.1 b/man/flac.1
index 0d130526..100274d9 100644
--- a/man/flac.1
+++ b/man/flac.1
@@ -74,6 +74,9 @@ Output files have their timestamps/permissions set to match those of their input
 \fB--keep-foreign-metadata \fR
 If encoding, save WAVE, RF64, or AIFF non-audio chunks in FLAC metadata.  If decoding, restore any saved non-audio chunks from FLAC metadata when writing the decoded file.  Foreign metadata cannot be transcoded, e.g. WAVE chunks saved in a FLAC file cannot be restored when decoding to AIFF.  Input and output must be regular files (not stdin or stdout).
 .TP
+\fB--keep-foreign-metadata-if-present \fR
+Like --keep-foreign-metadata, but without throwing an error if foreign metadata cannot be found or restored, instead printing a warning.
+.TP
 \fB--skip={\fI#\fB|\fImm:ss.ss\fB}\fR
 Skip over the first number of samples of the input.  This works for both encoding and decoding, but not testing.  The alternative form mm:ss.ss can be used to specify minutes, seconds, and fractions of a second.
 .TP
diff --git a/man/flac.sgml b/man/flac.sgml
index d1edf3a2..4aa0f094 100644
--- a/man/flac.sgml
+++ b/man/flac.sgml
@@ -223,6 +223,14 @@
 	</varlistentry>
 
 	<varlistentry>
+	  <term><option>--keep-foreign-metadata-if-present</option>
+	  </term>
+	  <listitem>
+	    <para>Like --keep-foreign-metadata, but without throwing an error if foreign metadata cannot be found or restored, instead printing a warning.</para>
+	  </listitem>
+	</varlistentry>
+
+	<varlistentry>
 	  <term><option>--skip</option>={<replaceable>#</replaceable>|<replaceable>mm:ss.ss</replaceable>}</term>
 	  <listitem>
 	    <para>Skip over the first number of samples of the input.  This works for both encoding and decoding, but not testing.  The alternative form mm:ss.ss can be used to specify minutes, seconds, and fractions of a second.</para>
diff --git a/man/metaflac.1 b/man/metaflac.1
index 0c1c66bc..1490dffe 100644
--- a/man/metaflac.1
+++ b/man/metaflac.1
@@ -200,8 +200,8 @@ number of channels.  The sample rate must be one of 8, 11.025,
 96, 112, 128, 144, 176.4, or 192kHz.
 .TP
 \fB--scan-replay-gain\fR
-Like --add-replay-gain, but only analyzes the files rather than
-writing them to the tags.
+Like --add-replay-gain, but only analyzes the files rather
+than writing them to the tags.
 .TP
 \fB--remove-replay-gain\fR
 Removes the ReplayGain tags.
diff --git a/src/flac/decode.c b/src/flac/decode.c
index a7d07210..aaf2c46a 100644
--- a/src/flac/decode.c
+++ b/src/flac/decode.c
@@ -42,6 +42,7 @@ typedef struct {
 	FLAC__bool treat_warnings_as_errors;
 	FLAC__bool continue_through_decode_errors;
 	FLAC__bool channel_map_none;
+	FLAC__bool relaxed_foreign_metadata_handling;
 
 	struct {
 		replaygain_synthesis_spec_t spec;
@@ -67,6 +68,7 @@ typedef struct {
 	FLAC__bool aborting_due_to_until; /* true if we intentionally abort decoding prematurely because we hit the --until point */
 	FLAC__bool aborting_due_to_unparseable; /* true if we abort decoding because we hit an unparseable frame */
 	FLAC__bool error_callback_suppress_messages; /* turn on to prevent repeating messages from the error callback */
+	FLAC__bool warn_user_about_foreign_metadata; /* to prevent more than one warning message per file */
 
 	FLAC__bool iff_headers_need_fixup;
 
@@ -98,7 +100,7 @@ static FLAC__bool is_big_endian_host_;
 /*
  * local routines
  */
-static FLAC__bool DecoderSession_construct(DecoderSession *d, FLAC__bool is_ogg, FLAC__bool use_first_serial_number, long serial_number, FileFormat format, FLAC__bool treat_warnings_as_errors, FLAC__bool continue_through_decode_errors, FLAC__bool channel_map_none, replaygain_synthesis_spec_t replaygain_synthesis_spec, FLAC__bool analysis_mode, analysis_options aopts, utils__SkipUntilSpecification *skip_specification, utils__SkipUntilSpecification *until_specification, utils__CueSpecification *cue_specification, foreign_metadata_t *foreign_metadata, const char *infilename, const char *outfilename);
+static FLAC__bool DecoderSession_construct(DecoderSession *d, FLAC__bool is_ogg, FLAC__bool use_first_serial_number, long serial_number, FileFormat format, FLAC__bool treat_warnings_as_errors, FLAC__bool continue_through_decode_errors, FLAC__bool channel_map_none, FLAC__bool relaxed_foreign_metadata_handling, replaygain_synthesis_spec_t replaygain_synthesis_spec, FLAC__bool analysis_mode, analysis_options aopts, utils__SkipUntilSpecification *skip_specification, utils__SkipUntilSpecification *until_specification, utils__CueSpecification *cue_specification, foreign_metadata_t *foreign_metadata, const char *infilename, const char *outfilename);
 static void DecoderSession_destroy(DecoderSession *d, FLAC__bool error_occurred);
 static FLAC__bool DecoderSession_init_decoder(DecoderSession *d, const char *infilename);
 static FLAC__bool DecoderSession_process(DecoderSession *d);
@@ -160,6 +162,7 @@ int flac__decode_file(const char *infilename, const char *outfilename, FLAC__boo
 			options.treat_warnings_as_errors,
 			options.continue_through_decode_errors,
 			options.channel_map_none,
+			options.relaxed_foreign_metadata_handling,
 			options.replaygain_synthesis_spec,
 			analysis_mode,
 			aopts,
@@ -183,7 +186,7 @@ int flac__decode_file(const char *infilename, const char *outfilename, FLAC__boo
 	return DecoderSession_finish_ok(&decoder_session);
 }
 
-FLAC__bool DecoderSession_construct(DecoderSession *d, FLAC__bool is_ogg, FLAC__bool use_first_serial_number, long serial_number, FileFormat format, FLAC__bool treat_warnings_as_errors, FLAC__bool continue_through_decode_errors, FLAC__bool channel_map_none, replaygain_synthesis_spec_t replaygain_synthesis_spec, FLAC__bool analysis_mode, analysis_options aopts, utils__SkipUntilSpecification *skip_specification, utils__SkipUntilSpecification *until_specification, utils__CueSpecification *cue_specification, foreign_metadata_t *foreign_metadata, const char *infilename, const char *outfilename)
+FLAC__bool DecoderSession_construct(DecoderSession *d, FLAC__bool is_ogg, FLAC__bool use_first_serial_number, long serial_number, FileFormat format, FLAC__bool treat_warnings_as_errors, FLAC__bool continue_through_decode_errors, FLAC__bool channel_map_none, FLAC__bool relaxed_foreign_metadata_handling, replaygain_synthesis_spec_t replaygain_synthesis_spec, FLAC__bool analysis_mode, analysis_options aopts, utils__SkipUntilSpecification *skip_specification, utils__SkipUntilSpecification *until_specification, utils__CueSpecification *cue_specification, foreign_metadata_t *foreign_metadata, const char *infilename, const char *outfilename)
 {
 #if FLAC__HAS_OGG
 	d->is_ogg = is_ogg;
@@ -199,6 +202,7 @@ FLAC__bool DecoderSession_construct(DecoderSession *d, FLAC__bool is_ogg, FLAC__
 	d->treat_warnings_as_errors = treat_warnings_as_errors;
 	d->continue_through_decode_errors = continue_through_decode_errors;
 	d->channel_map_none = channel_map_none;
+	d->relaxed_foreign_metadata_handling = relaxed_foreign_metadata_handling;
 	d->replaygain.spec = replaygain_synthesis_spec;
 	d->replaygain.apply = false;
 	d->replaygain.scale = 0.0;
@@ -220,6 +224,10 @@ FLAC__bool DecoderSession_construct(DecoderSession *d, FLAC__bool is_ogg, FLAC__
 	d->aborting_due_to_until = false;
 	d->aborting_due_to_unparseable = false;
 	d->error_callback_suppress_messages = false;
+	if(relaxed_foreign_metadata_handling)
+		d->warn_user_about_foreign_metadata = false;
+	else
+		d->warn_user_about_foreign_metadata = true;
 
 	d->iff_headers_need_fixup = false;
 
@@ -296,8 +304,20 @@ FLAC__bool DecoderSession_init_decoder(DecoderSession *decoder_session, const ch
 	if(!decoder_session->analysis_mode && !decoder_session->test_only && decoder_session->foreign_metadata) {
 		const char *error;
 		if(!flac__foreign_metadata_read_from_flac(decoder_session->foreign_metadata, infilename, &error)) {
-			flac__utils_printf(stderr, 1, "%s: ERROR reading foreign metadata: %s\n", decoder_session->inbasefilename, error);
-			return false;
+			if(decoder_session->relaxed_foreign_metadata_handling) {
+				flac__utils_printf(stderr, 1, "%s: WARNING reading foreign metadata: %s\n", decoder_session->inbasefilename, error);
+				if(decoder_session->treat_warnings_as_errors) {
+					return false;
+				}
+				else {
+					/* Couldn't find foreign metadata, stop processing */
+					decoder_session->foreign_metadata = 0;
+				}
+			}
+			else {
+				flac__utils_printf(stderr, 1, "%s: ERROR reading foreign metadata: %s\n", decoder_session->inbasefilename, error);
+				return false;
+			}
 		}
 	}
 
@@ -314,6 +334,12 @@ FLAC__bool DecoderSession_init_decoder(DecoderSession *decoder_session, const ch
 	if (decoder_session->replaygain.spec.apply || !decoder_session->channel_map_none)
 		FLAC__stream_decoder_set_metadata_respond(decoder_session->decoder, FLAC__METADATA_TYPE_VORBIS_COMMENT);
 
+	if(!decoder_session->analysis_mode && !decoder_session->test_only && decoder_session->foreign_metadata == NULL)
+		/* Warn user if foreign metadata is found */
+		for(uint32_t i = 0; i < FLAC__FOREIGN_METADATA_NUMBER_OF_RECOGNIZED_APPLICATION_IDS; i++)
+			FLAC__stream_decoder_set_metadata_respond_application(decoder_session->decoder, (FLAC__byte *)FLAC__FOREIGN_METADATA_APPLICATION_ID[i]);
+
+
 #if FLAC__HAS_OGG
 	if(decoder_session->is_ogg) {
 		if(!decoder_session->use_first_serial_number)
@@ -1449,6 +1475,11 @@ void metadata_callback(const FLAC__StreamDecoder *decoder, const FLAC__StreamMet
 		}
 		(void)flac__utils_get_channel_mask_tag(metadata, &decoder_session->channel_mask);
 	}
+	else if(metadata->type == FLAC__METADATA_TYPE_APPLICATION && decoder_session->warn_user_about_foreign_metadata) {
+		/* Foreign metadata signalling */
+		flac__utils_printf(stderr, 1, "%s: WARNING: found foreign metadata, use --keep-foreign-metadata to restore\n", decoder_session->inbasefilename);
+		decoder_session->warn_user_about_foreign_metadata = false;
+	}
 }
 
 void error_callback(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
diff --git a/src/flac/decode.h b/src/flac/decode.h
index 6a90bfc6..bd93fd6a 100644
--- a/src/flac/decode.h
+++ b/src/flac/decode.h
@@ -52,6 +52,7 @@ typedef struct {
 	FLAC__bool has_cue_specification;
 	utils__CueSpecification cue_specification;
 	FLAC__bool channel_map_none; /* --channel-map=none specified, eventually will expand to take actual channel map */
+	FLAC__bool relaxed_foreign_metadata_handling;
 
 	FileFormat format;
 	union {
diff --git a/src/flac/encode.c b/src/flac/encode.c
index 26812030..7dc226af 100644
--- a/src/flac/encode.c
+++ b/src/flac/encode.c
@@ -978,8 +978,15 @@ int flac__encode_file(FILE *infile, FLAC__off_t infilesize, const char *infilena
 				flac__foreign_metadata_read_from_wave64(options.format_options.iff.foreign_metadata, infilename, &error) :
 				flac__foreign_metadata_read_from_aiff(options.format_options.iff.foreign_metadata, infilename, &error)
 		)) {
-			flac__utils_printf(stderr, 1, "%s: ERROR reading foreign metadata: %s\n", encoder_session.inbasefilename, error);
-			return EncoderSession_finish_error(&encoder_session);
+			if(options.relaxed_foreign_metadata_handling) {
+				flac__utils_printf(stderr, 1, "%s: WARNING reading foreign metadata: %s\n", encoder_session.inbasefilename, error);
+				if(encoder_session.treat_warnings_as_errors)
+					return EncoderSession_finish_error(&encoder_session);
+			}
+			else {
+				flac__utils_printf(stderr, 1, "%s: ERROR reading foreign metadata: %s\n", encoder_session.inbasefilename, error);
+				return EncoderSession_finish_error(&encoder_session);
+			}
 		}
 	}
 
diff --git a/src/flac/encode.h b/src/flac/encode.h
index b0efda8a..1ae19449 100644
--- a/src/flac/encode.h
+++ b/src/flac/encode.h
@@ -86,6 +86,7 @@ typedef struct {
 	FLAC__bool sector_align;
 	FLAC__bool error_on_compression_fail;
 	FLAC__bool limit_min_bitrate;
+	FLAC__bool relaxed_foreign_metadata_handling;
 
 	FLAC__StreamMetadata *vorbis_comment;
 	FLAC__StreamMetadata *vorbis_comment_with_channel_mask_tag;
diff --git a/src/flac/foreign_metadata.c b/src/flac/foreign_metadata.c
index 9ad9c185..72ba3386 100644
--- a/src/flac/foreign_metadata.c
+++ b/src/flac/foreign_metadata.c
@@ -35,8 +35,7 @@
 #endif
 #define min(x,y) ((x)<(y)?(x):(y))
 
-
-static const char *FLAC__FOREIGN_METADATA_APPLICATION_ID[3] = { "aiff" , "riff", "w64 " };
+const char *FLAC__FOREIGN_METADATA_APPLICATION_ID[FLAC__FOREIGN_METADATA_NUMBER_OF_RECOGNIZED_APPLICATION_IDS] = { "aiff" , "riff", "w64 " };
 
 static FLAC__uint32 unpack32be_(const FLAC__byte *b)
 {
@@ -474,7 +473,8 @@ static FLAC__bool read_from_flac_(foreign_metadata_t *fm, FILE *f, FLAC__Metadat
 {
 	FLAC__byte id[4], buffer[12];
 	FLAC__off_t offset;
-	FLAC__bool type_found = false, ds64_found = false;
+	FLAC__bool foreign_metadata_found = false, type_found = false, ds64_found = false;
+	uint32_t foreign_metadata_found_type = 0;
 
 	FLAC__ASSERT(FLAC__STREAM_METADATA_APPLICATION_ID_LEN == sizeof(id)*8);
 
@@ -485,8 +485,17 @@ static FLAC__bool read_from_flac_(foreign_metadata_t *fm, FILE *f, FLAC__Metadat
 			if(error) *error = "FLAC__metadata_simple_iterator_get_application_id() error (002)";
 			return false;
 		}
-		if(memcmp(id, FLAC__FOREIGN_METADATA_APPLICATION_ID[fm->type], sizeof(id)))
+		if(memcmp(id, FLAC__FOREIGN_METADATA_APPLICATION_ID[fm->type], sizeof(id))) {
+			/* The found application metadata block is not of the right type, check
+			 * whether it is of another recognized type so we can tell the user it
+			 * is decoding to the wrong file format */
+			for(uint32_t i = 0; i < FLAC__FOREIGN_METADATA_NUMBER_OF_RECOGNIZED_APPLICATION_IDS; i++)
+				if(memcmp(id, FLAC__FOREIGN_METADATA_APPLICATION_ID[i], sizeof(id)) == 0) {
+					foreign_metadata_found = true;
+					foreign_metadata_found_type = i;
+				}
 			continue;
+		}
 		offset = FLAC__metadata_simple_iterator_get_block_offset(it);
 		/* skip over header and app ID */
 		offset += (FLAC__STREAM_METADATA_IS_LAST_LEN + FLAC__STREAM_METADATA_TYPE_LEN + FLAC__STREAM_METADATA_LENGTH_LEN) / 8;
@@ -614,8 +623,21 @@ static FLAC__bool read_from_flac_(foreign_metadata_t *fm, FILE *f, FLAC__Metadat
 			return false;
 	}
 	if(!type_found) {
-		if(error) *error = "no foreign metadata found (022)";
-		return false;
+		if(foreign_metadata_found) {
+			if(error) {
+				if(foreign_metadata_found_type == 0 /*"aiff"*/)
+					*error = "found foreign metadata of wrong type, try decoding to AIFF instead";
+				else if(foreign_metadata_found_type == 1 /*"riff"*/)
+					*error = "found foreign metadata of wrong type, try decoding to WAV or RF64 instead";
+				else if(foreign_metadata_found_type == 2 /*"w64 "*/)
+					*error = "found foreign metadata of wrong type, try decoding to WAVE64 instead";
+			}
+			return false;
+		}
+		else {
+			if(error) *error = "no foreign metadata found (022)";
+			return false;
+		}
 	}
 	if(fm->is_rf64 && !ds64_found) {
 		if(error) *error = "invalid RF64 file: second chunk is not \"ds64\" (023)";
diff --git a/src/flac/foreign_metadata.h b/src/flac/foreign_metadata.h
index e5a17dd1..cb433d84 100644
--- a/src/flac/foreign_metadata.h
+++ b/src/flac/foreign_metadata.h
@@ -28,6 +28,10 @@
 #include "utils.h"
 #include "share/compat.h"
 
+#define FLAC__FOREIGN_METADATA_NUMBER_OF_RECOGNIZED_APPLICATION_IDS 3
+
+extern const char *FLAC__FOREIGN_METADATA_APPLICATION_ID[FLAC__FOREIGN_METADATA_NUMBER_OF_RECOGNIZED_APPLICATION_IDS];
+
 /* WATCHOUT: these enums are used to index internal arrays */
 typedef enum {
 	FOREIGN_BLOCK_TYPE__AIFF = 0, /* for AIFF and AIFF-C */
diff --git a/src/flac/main.c b/src/flac/main.c
index 9a972021..906457dc 100644
--- a/src/flac/main.c
+++ b/src/flac/main.c
@@ -90,25 +90,26 @@ static struct share__option long_options_[] = {
 	/*
 	 * general options
 	 */
-	{ "help"                  , share__no_argument, 0, 'h' },
-	{ "explain"               , share__no_argument, 0, 'H' },
-	{ "version"               , share__no_argument, 0, 'v' },
-	{ "decode"                , share__no_argument, 0, 'd' },
-	{ "analyze"               , share__no_argument, 0, 'a' },
-	{ "test"                  , share__no_argument, 0, 't' },
-	{ "stdout"                , share__no_argument, 0, 'c' },
-	{ "silent"                , share__no_argument, 0, 's' },
-	{ "totally-silent"        , share__no_argument, 0, 0 },
-	{ "warnings-as-errors"    , share__no_argument, 0, 'w' },
-	{ "force"                 , share__no_argument, 0, 'f' },
-	{ "delete-input-file"     , share__no_argument, 0, 0 },
-	{ "preserve-modtime"      , share__no_argument, 0, 0 },
-	{ "keep-foreign-metadata" , share__no_argument, 0, 0 },
-	{ "output-prefix"         , share__required_argument, 0, 0 },
-	{ "output-name"           , share__required_argument, 0, 'o' },
-	{ "skip"                  , share__required_argument, 0, 0 },
-	{ "until"                 , share__required_argument, 0, 0 },
-	{ "channel-map"           , share__required_argument, 0, 0 }, /* undocumented */
+	{ "help"                             , share__no_argument, 0, 'h' },
+	{ "explain"                          , share__no_argument, 0, 'H' },
+	{ "version"                          , share__no_argument, 0, 'v' },
+	{ "decode"                           , share__no_argument, 0, 'd' },
+	{ "analyze"                          , share__no_argument, 0, 'a' },
+	{ "test"                             , share__no_argument, 0, 't' },
+	{ "stdout"                           , share__no_argument, 0, 'c' },
+	{ "silent"                           , share__no_argument, 0, 's' },
+	{ "totally-silent"                   , share__no_argument, 0, 0 },
+	{ "warnings-as-errors"               , share__no_argument, 0, 'w' },
+	{ "force"                            , share__no_argument, 0, 'f' },
+	{ "delete-input-file"                , share__no_argument, 0, 0 },
+	{ "preserve-modtime"                 , share__no_argument, 0, 0 },
+	{ "keep-foreign-metadata"            , share__no_argument, 0, 0 },
+	{ "keep-foreign-metadata-if-present" , share__no_argument, 0, 0 },
+	{ "output-prefix"                    , share__required_argument, 0, 0 },
+	{ "output-name"                      , share__required_argument, 0, 'o' },
+	{ "skip"                             , share__required_argument, 0, 0 },
+	{ "until"                            , share__required_argument, 0, 0 },
+	{ "channel-map"                      , share__required_argument, 0, 0 }, /* undocumented */
 
 	/*
 	 * decoding options
@@ -244,6 +245,7 @@ static struct {
 	FLAC__bool delete_input;
 	FLAC__bool preserve_modtime;
 	FLAC__bool keep_foreign_metadata;
+	FLAC__bool keep_foreign_metadata_if_present;
 	FLAC__bool replay_gain;
 	FLAC__bool ignore_chunk_sizes;
 	FLAC__bool sector_align;
@@ -468,7 +470,7 @@ int do_it(void)
 		if(!option_values.mode_decode && 0 != option_values.cuesheet_filename && option_values.num_files > 1) {
 			return usage_error("ERROR: --cuesheet cannot be used when encoding multiple files\n");
 		}
-		if(option_values.keep_foreign_metadata) {
+		if(option_values.keep_foreign_metadata || option_values.keep_foreign_metadata_if_present) {
 			/* we're not going to try and support the re-creation of broken WAVE files */
 			if(option_values.ignore_chunk_sizes)
 				return usage_error("ERROR: using --keep-foreign-metadata cannot be used with --ignore-chunk-sizes\n");
@@ -572,6 +574,7 @@ FLAC__bool init_options(void)
 	option_values.delete_input = false;
 	option_values.preserve_modtime = true;
 	option_values.keep_foreign_metadata = false;
+	option_values.keep_foreign_metadata_if_present = false;
 	option_values.replay_gain = false;
 	option_values.ignore_chunk_sizes = false;
 	option_values.sector_align = false;
@@ -675,6 +678,9 @@ int parse_option(int short_option, const char *long_option, const char *option_a
 		else if(0 == strcmp(long_option, "keep-foreign-metadata")) {
 			option_values.keep_foreign_metadata = true;
 		}
+		else if(0 == strcmp(long_option, "keep-foreign-metadata-if-present")) {
+			option_values.keep_foreign_metadata_if_present = true;
+		}
 		else if(0 == strcmp(long_option, "output-prefix")) {
 			FLAC__ASSERT(0 != option_argument);
 			option_values.output_prefix = option_argument;
@@ -855,6 +861,7 @@ int parse_option(int short_option, const char *long_option, const char *option_a
 		}
 		else if(0 == strcmp(long_option, "no-keep-foreign-metadata")) {
 			option_values.keep_foreign_metadata = false;
+			option_values.keep_foreign_metadata_if_present = false;
 		}
 		else if(0 == strcmp(long_option, "no-replay-gain")) {
 			option_values.replay_gain = false;
@@ -1257,6 +1264,8 @@ void show_help(void)
 	printf("      --delete-input-file      Deletes after a successful encode/decode\n");
 	printf("      --preserve-modtime       Output files keep timestamp of input (default)\n");
 	printf("      --keep-foreign-metadata  Save/restore WAVE or AIFF non-audio chunks\n");
+	printf("      --keep-foreign-metadata-if-present  Save/restore WAVE or AIFF non-audio\n");
+	printf("                        but not return an error when no such chunks are found\n");
 	printf("      --skip={#|mm:ss.ss}      Skip the given initial samples for each input\n");
 	printf("      --until={#|[+|-]mm:ss.ss}  Stop at the given sample for each input file\n");
 #if FLAC__HAS_OGG
@@ -1410,6 +1419,12 @@ void show_explain(void)
 	printf("                               transcoded, e.g. WAVE chunks saved in a FLAC file\n");
 	printf("                               cannot be restored when decoding to AIFF.  Input\n");
 	printf("                               and output must be regular files, not stdin/out.\n");
+	printf("      --keep-foreign-metadata-if-present  As previous option, but do not throw\n");
+	printf("                               an error in case no foreign metadata is found,\n");
+	printf("                               the wrong kind of foreign metadata is found (on\n");
+	printf("                               decoding) or if the foreign could not be parsed,\n");
+	printf("                               i.e. all foreign metadata related errors are\n");
+	printf("                               treated as warnings.\n");
 	printf("      --skip={#|mm:ss.ss}      Skip the first # samples of each input file; can\n");
 	printf("                               be used both for encoding and decoding.  The\n");
 	printf("                               alternative form mm:ss.ss can be used to specify\n");
@@ -1803,7 +1818,7 @@ int encode_file(const char *infilename, FLAC__bool is_first_file, FLAC__bool is_
 		}
 	}
 
-	if(option_values.keep_foreign_metadata) {
+	if(option_values.keep_foreign_metadata || option_values.keep_foreign_metadata_if_present) {
 		if(encode_infile == stdin || option_values.force_to_stdout) {
 			conditional_fclose(encode_infile);
 			return usage_error("ERROR: --keep-foreign-metadata cannot be used when encoding from stdin or to stdout\n");
@@ -1946,6 +1961,7 @@ int encode_file(const char *infilename, FLAC__bool is_first_file, FLAC__bool is_
 	encode_options.debug.do_md5 = option_values.debug.do_md5;
 	encode_options.error_on_compression_fail = option_values.error_on_compression_fail;
 	encode_options.limit_min_bitrate = option_values.limit_min_bitrate;
+	encode_options.relaxed_foreign_metadata_handling = option_values.keep_foreign_metadata_if_present;
 
 	/* if infilename and outfilename point to the same file, we need to write to a temporary file */
 	if(encode_infile != stdin && grabbag__file_are_same(infilename, outfilename)) {
@@ -1976,7 +1992,7 @@ int encode_file(const char *infilename, FLAC__bool is_first_file, FLAC__bool is_
 		encode_options.format_options.iff.foreign_metadata = 0;
 
 		/* initialize foreign metadata if requested */
-		if(option_values.keep_foreign_metadata) {
+		if(option_values.keep_foreign_metadata || option_values.keep_foreign_metadata_if_present) {
 			encode_options.format_options.iff.foreign_metadata =
 				flac__foreign_metadata_new(
 					input_format==FORMAT_WAVE || input_format==FORMAT_RF64?
@@ -2102,7 +2118,7 @@ int decode_file(const char *infilename)
 			return usage_error("ERROR: for decoding to a raw file you must specify a value for --endian and --sign\n");
 	}
 
-	if(option_values.keep_foreign_metadata) {
+	if(option_values.keep_foreign_metadata || option_values.keep_foreign_metadata_if_present) {
 		if(0 == strcmp(infilename, "-") || 0 == strcmp(outfilename, "-"))
 			return usage_error("ERROR: --keep-foreign-metadata cannot be used when decoding from stdin or to stdout\n");
 		if(output_format != FORMAT_WAVE && output_format != FORMAT_WAVE64 && output_format != FORMAT_RF64 && output_format != FORMAT_AIFF && output_format != FORMAT_AIFF_C)
@@ -2145,6 +2161,7 @@ int decode_file(const char *infilename)
 
 	decode_options.treat_warnings_as_errors = option_values.treat_warnings_as_errors;
 	decode_options.continue_through_decode_errors = option_values.continue_through_decode_errors;
+	decode_options.relaxed_foreign_metadata_handling = option_values.keep_foreign_metadata_if_present;
 	decode_options.replaygain_synthesis_spec = option_values.replaygain_synthesis_spec;
 #if FLAC__HAS_OGG
 	decode_options.is_ogg = treat_as_ogg;
@@ -2164,7 +2181,7 @@ int decode_file(const char *infilename)
 		decode_options.format_options.iff.foreign_metadata = 0;
 
 		/* initialize foreign metadata if requested */
-		if(option_values.keep_foreign_metadata) {
+		if(option_values.keep_foreign_metadata || option_values.keep_foreign_metadata_if_present) {
 			decode_options.format_options.iff.foreign_metadata =
 				flac__foreign_metadata_new(
 					output_format==FORMAT_WAVE || output_format==FORMAT_RF64?