Write sample_aspect_ratio to asf files.

Fixes ticket #3528.

libavformat/asfenc.c

@@ -352,7 +352,7 @@ static int asf_write_header1(AVFormatContext *s, int64_t file_size,
     AVIOContext *pb = s->pb;
     AVDictionaryEntry *tags[5];
     int header_size, n, extra_size, extra_size2, wav_extra_size, file_time;
-    int has_title;
+    int has_title, has_aspect_ratio = 0;
     int metadata_count;
     AVCodecContext *enc;
     int64_t header_offset, cur_pos, hpos;
@@ -378,6 +378,10 @@ static int asf_write_header1(AVFormatContext *s, int64_t file_size,
         avpriv_set_pts_info(s->streams[n], 32, 1, 1000); /* 32 bit pts in ms */
 
         bit_rate += enc->bit_rate;
+        if (   enc->codec_type == AVMEDIA_TYPE_VIDEO
+            && enc->sample_aspect_ratio.num > 0
+            && enc->sample_aspect_ratio.den > 0)
+            has_aspect_ratio++;
     }
 
     if (asf->is_streamed) {
@@ -410,8 +414,40 @@ static int asf_write_header1(AVFormatContext *s, int64_t file_size,
     /* unknown headers */
     hpos = put_header(pb, &ff_asf_head1_guid);
     ff_put_guid(pb, &ff_asf_head2_guid);
-    avio_wl32(pb, 6);
+    avio_wl16(pb, 6);
-    avio_wl16(pb, 0);
+    if (has_aspect_ratio) {
+        int64_t hpos2;
+        avio_wl32(pb, 26 + has_aspect_ratio * 84);
+        hpos2 = put_header(pb, &ff_asf_metadata_header);
+        avio_wl16(pb, 2 * has_aspect_ratio);
+        for (n = 0; n < s->nb_streams; n++) {
+            enc = s->streams[n]->codec;
+            if (   enc->codec_type == AVMEDIA_TYPE_VIDEO
+                && enc->sample_aspect_ratio.num > 0
+                && enc->sample_aspect_ratio.den > 0) {
+                AVRational sar = enc->sample_aspect_ratio;
+                avio_wl16(pb, 0);
+                // the stream number is set like this below
+                avio_wl16(pb, n + 1);
+                avio_wl16(pb, 26); // name_len
+                avio_wl16(pb,  3); // value_type
+                avio_wl32(pb,  4); // value_len
+                avio_put_str16le(pb, "AspectRatioX");
+                avio_wl32(pb, sar.num);
+                avio_wl16(pb, 0);
+                // the stream number is set like this below
+                avio_wl16(pb, n + 1);
+                avio_wl16(pb, 26); // name_len
+                avio_wl16(pb,  3); // value_type
+                avio_wl32(pb,  4); // value_len
+                avio_put_str16le(pb, "AspectRatioY");
+                avio_wl32(pb, sar.den);
+            }
+        }
+        end_header(pb, hpos2);
+    } else {
+        avio_wl32(pb, 0);
+    }
     end_header(pb, hpos);
 
     /* title and other infos */