use asf stream information to set bitrate

patch by Zuxy Meng zuxy dot meng chez gmail tod com
reference thread: [Ffmpeg-devel] Third Try: Set bit_rate for asf format

Originally committed as revision 8861 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/asf.c

@@ -145,8 +145,10 @@ static int asf_read_header(AVFormatContext *s, AVFormatParameters *ap)
     int size, i;
     int64_t gsize;
     AVRational dar[128];
+    uint32_t bitrate[128];
 
     memset(dar, 0, sizeof(dar));
+    memset(bitrate, 0, sizeof(bitrate));
 
     get_guid(pb, &g);
     if (memcmp(&g, &asf_header, sizeof(GUID)))
@@ -421,13 +423,13 @@ static int asf_read_header(AVFormatContext *s, AVFormatParameters *ap)
             }
         } else if (!memcmp(&g, &ext_stream_header, sizeof(GUID))) {
             int ext_len, payload_ext_ct, stream_ct;
-            uint32_t ext_d;
+            uint32_t ext_d, leak_rate, stream_num;
             int64_t pos_ex_st;
             pos_ex_st = url_ftell(pb);
 
             get_le64(pb); // starttime
             get_le64(pb); // endtime
-            get_le32(pb); // leak-datarate
+            leak_rate = get_le32(pb); // leak-datarate
             get_le32(pb); // bucket-datasize
             get_le32(pb); // init-bucket-fullness
             get_le32(pb); // alt-leak-datarate
@@ -435,12 +437,15 @@ static int asf_read_header(AVFormatContext *s, AVFormatParameters *ap)
             get_le32(pb); // alt-init-bucket-fullness
             get_le32(pb); // max-object-size
             get_le32(pb); // flags (reliable,seekable,no_cleanpoints?,resend-live-cleanpoints, rest of bits reserved)
-            get_le16(pb); // stream-num
+            stream_num = get_le16(pb); // stream-num
             get_le16(pb); // stream-language-id-index
             get_le64(pb); // avg frametime in 100ns units
             stream_ct = get_le16(pb); //stream-name-count
             payload_ext_ct = get_le16(pb); //payload-extension-system-count
 
+            if (stream_num < 128)
+                bitrate[stream_num] = leak_rate;
+
             for (i=0; i<stream_ct; i++){
                 get_le16(pb);
                 ext_len = get_le16(pb);
@@ -504,8 +509,11 @@ static int asf_read_header(AVFormatContext *s, AVFormatParameters *ap)
 
     for(i=0; i<128; i++){
         int stream_num= asf->asfid2avid[i];
-        if(stream_num>=0 && dar[i].num>0 && dar[i].den>0){
+        if(stream_num>=0){
             AVCodecContext *codec= s->streams[stream_num]->codec;
+            if (!codec->bit_rate)
+                codec->bit_rate = bitrate[i];
+            if (dar[i].num > 0 && dar[i].den > 0)
             av_reduce(&codec->sample_aspect_ratio.num,
                     &codec->sample_aspect_ratio.den,
                     dar[i].num, dar[i].den, INT_MAX);