mp3enc: allow omitting the id3v2 header with -id3v2_version 0

doc/muxers.texi

@@ -434,8 +434,10 @@ avconv -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut
 
 The MP3 muxer writes a raw MP3 stream with an ID3v2 header at the beginning and
 optionally an ID3v1 tag at the end. ID3v2.3 and ID3v2.4 are supported, the
-@code{id3v2_version} option controls which one is used. The legacy ID3v1 tag is
-not written by default, but may be enabled with the @code{write_id3v1} option.
+@code{id3v2_version} option controls which one is used. Setting
+@code{id3v2_version} to 0 will disable the ID3v2 header completely. The legacy
+ID3v1 tag is not written by default, but may be enabled with the
+@code{write_id3v1} option.
 
 The muxer may also write a Xing frame at the beginning, which contains the
 number of frames in the file. It is useful for computing duration of VBR files.
@@ -466,6 +468,11 @@ avconv -i input.mp3 -i cover.png -c copy -metadata:s:v title="Album cover"
 -metadata:s:v comment="Cover (Front)" out.mp3
 @end example
 
+Write a "clean" MP3 without any extra features:
+@example
+avconv -i input.wav -write_xing 0 -id3v2_version 0 out.mp3
+@end example
+
 @section ogg
 
 Ogg container muxer.

libavformat/mp3enc.c

@@ -319,7 +319,7 @@ AVOutputFormat ff_mp2_muxer = {
 
 static const AVOption options[] = {
     { "id3v2_version", "Select ID3v2 version to write. Currently 3 and 4 are supported.",
-      offsetof(MP3Context, id3v2_version), AV_OPT_TYPE_INT, {.i64 = 4}, 3, 4, AV_OPT_FLAG_ENCODING_PARAM},
+      offsetof(MP3Context, id3v2_version), AV_OPT_TYPE_INT, {.i64 = 4}, 0, 4, AV_OPT_FLAG_ENCODING_PARAM},
     { "write_id3v1", "Enable ID3v1 writing. ID3v1 tags are written in UTF-8 which may not be supported by most software.",
       offsetof(MP3Context, write_id3v1), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
     { "write_xing",  "Write the Xing header containing file duration.",
@@ -392,6 +392,14 @@ static int mp3_write_header(struct AVFormatContext *s)
     MP3Context  *mp3 = s->priv_data;
     int ret, i;
 
+    if (mp3->id3v2_version      &&
+        mp3->id3v2_version != 3 &&
+        mp3->id3v2_version != 4) {
+        av_log(s, AV_LOG_ERROR, "Invalid ID3v2 version requested: %d. Only "
+               "3, 4 or 0 (disabled) are allowed.\n", mp3->id3v2_version);
+        return AVERROR(EINVAL);
+    }
+
     /* check the streams -- we want exactly one audio and arbitrary number of
      * video (attached pictures) */
     mp3->audio_stream_idx = -1;
@@ -415,13 +423,22 @@ static int mp3_write_header(struct AVFormatContext *s)
     }
     mp3->pics_to_write = s->nb_streams - 1;
 
-    ff_id3v2_start(&mp3->id3, s->pb, mp3->id3v2_version, ID3v2_DEFAULT_MAGIC);
-    ret = ff_id3v2_write_metadata(s, &mp3->id3);
-    if (ret < 0)
-        return ret;
+    if (mp3->pics_to_write && !mp3->id3v2_version) {
+        av_log(s, AV_LOG_ERROR, "Attached pictures were requested, but the "
+               "ID3v2 header is disabled.\n");
+        return AVERROR(EINVAL);
+    }
+
+    if (mp3->id3v2_version) {
+        ff_id3v2_start(&mp3->id3, s->pb, mp3->id3v2_version, ID3v2_DEFAULT_MAGIC);
+        ret = ff_id3v2_write_metadata(s, &mp3->id3);
+        if (ret < 0)
+            return ret;
+    }
 
     if (!mp3->pics_to_write) {
-        ff_id3v2_finish(&mp3->id3, s->pb);
+        if (mp3->id3v2_version)
+            ff_id3v2_finish(&mp3->id3, s->pb);
         mp3_write_xing(s);
     }
 

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFORMAT_VERSION_MAJOR 55
 #define LIBAVFORMAT_VERSION_MINOR 10
-#define LIBAVFORMAT_VERSION_MICRO  2
+#define LIBAVFORMAT_VERSION_MICRO  3
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \