[FFmpeg-devel] Subject: [PATCH] Process compressed id3v2 tags.

[Adrian Drzewiecki]

ID3v2.4 allows for zlib compressed tags, but libavformat skips them.
Implement code to inflate compressed tags.
---
 libavformat/id3v2.c |   97 ++++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 89 insertions(+), 8 deletions(-)

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index bb8819f..651b1db 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -33,6 +33,8 @@
 #include "libavutil/dict.h"
 #include "avio_internal.h"

+#include <zlib.h>
+
 const AVMetadataConv ff_id3v2_34_metadata_conv[] = {
     { "TALB", "album"},
     { "TCOM", "composer"},
@@ -419,6 +421,16 @@ static const ID3v2EMFunc
*get_extra_meta_func(const char *tag, int isv34)
     return &id3v2_extra_meta_funcs[i];
 }

+static void *ff_id3v2_zalloc(void *opaque, unsigned int items,
unsigned int size)
+{
+    return av_malloc(items * size);
+}
+
+static void ff_id3v2_zfree(void *opaque, void *ptr)
+{
+    av_free(ptr);
+}
+
 static void ff_id3v2_parse(AVFormatContext *s, int len, uint8_t
version, uint8_t flags, ID3v2ExtraMeta **extra_meta)
 {
     int isv34, unsync;
@@ -476,6 +488,8 @@ static void ff_id3v2_parse(AVFormatContext *s, int
len, uint8_t version, uint8_t
     while (len >= taghdrlen) {
         unsigned int tflags = 0;
         int tunsync = 0;
+	int tcomp = 0;
+	int dlen;

         if (isv34) {
             avio_read(s->pb, tag, 4);
@@ -509,24 +523,91 @@ static void ff_id3v2_parse(AVFormatContext *s,
int len, uint8_t version, uint8_t
         if (tflags & ID3v2_FLAG_DATALEN) {
             if (tlen < 4)
                 break;
-            avio_rb32(s->pb);
+            dlen = avio_rb32(s->pb);
             tlen -= 4;
-        }
+        } else
+            dlen = tlen;
+
+	tcomp = tflags & ID3v2_FLAG_COMPRESSION;

-        if (tflags & (ID3v2_FLAG_ENCRYPTION | ID3v2_FLAG_COMPRESSION)) {
-            av_log(s, AV_LOG_WARNING, "Skipping encrypted/compressed
ID3v2 frame %s.\n", tag);
+        if (tflags & ID3v2_FLAG_ENCRYPTION) {
+            av_log(s, AV_LOG_WARNING, "Skipping encrypted ID3v2 frame
%s.\n", tag);
             avio_skip(s->pb, tlen);
         /* check for text tag or supported special meta tag */
         } else if (tag[0] == 'T' || (extra_meta && (extra_func =
get_extra_meta_func(tag, isv34)))) {
-            if (unsync || tunsync) {
+            if (unsync || tunsync || tcomp) {
                 int i, j;
-                av_fast_malloc(&buffer, &buffer_size, tlen);
+                av_fast_malloc(&buffer, &buffer_size, dlen);
                 if (!buffer) {
                     av_log(s, AV_LOG_ERROR, "Failed to alloc %d
bytes\n", tlen);
                     goto seek;
                 }
-                for (i = 0, j = 0; i < tlen; i++, j++) {
-                    buffer[j] = avio_r8(s->pb);
+                if (tcomp) {
+                    z_stream zstrm;
+                    int err;
+
+                    av_log(s, AV_LOG_INFO, "Compresssed frame %s
tlen=%d dlen=%d\n", tag, tlen, dlen);
+
+                    zstrm.next_in = NULL;
+                    zstrm.avail_in = 0;
+                    zstrm.zalloc = ff_id3v2_zalloc;
+                    zstrm.zfree = ff_id3v2_zfree;
+                    zstrm.next_out = buffer;
+                    zstrm.avail_out = buffer_size;
+
+                    err = inflateInit(&zstrm);
+                    if (err != Z_OK) {
+                        av_log(s, AV_LOG_ERROR, "inflate init failed:
%d\n", err);
+                        goto seek;
+                    }
+
+                    for (;;) {
+                        char buf[4096];
+                        int n, end;
+
+                        n = sizeof *buf;
+                        if (n > tlen)
+                            n = tlen;
+
+                        n = avio_read(s->pb, buf, n);
+                        if (n < 0) {
+                            av_log(s, AV_LOG_ERROR, "read failed\n");
+                            goto seek;
+                        }
+
+                        tlen -= n;
+
+                        zstrm.next_in = buf;
+                        zstrm.avail_in = n;
+
+                        end = (zstrm.avail_out == 0);
+
+                        err = inflate(&zstrm, Z_SYNC_FLUSH);
+                        if (err == Z_STREAM_END) {
+                            inflateEnd(&zstrm);
+                            break;
+                        }
+                        if (err != Z_OK) {
+                            av_log(s, AV_LOG_ERROR, "inflate failed;
%d\n", err);
+                            inflateEnd(&zstrm);
+                            goto seek;
+                        }
+                        if (!tlen) {
+                            av_log(s, AV_LOG_ERROR, "inflate reached
end of tag\n");
+                            inflateEnd(&zstrm);
+                            goto seek;
+                        }
+                        if (end) {
+                            av_log(s, AV_LOG_ERROR, "expected end of
uncompressed data\n");
+                            inflateEnd(&zstrm);
+                            goto seek;
+                        }
+                    }
+                }
+
+                for (i = 0, j = 0; i < dlen; i++, j++) {
+                    if (!tcomp)
+                        buffer[j] = avio_r8(s->pb);
                     if (j > 0 && !buffer[j] && buffer[j - 1] == 0xff) {
                         /* Unsynchronised byte, skip it */
                         j--;
-- 
1.7.7.4