avfotmat/whip: add support to handle multi NACK in a bundled packet

Signed-off-by: Jack Lau <jacklau1222@qq.com>

Author: JackLau1222

libavformat/whip.c

@@ -154,7 +154,7 @@
 /** 
  * Retransmission / NACK support
 */
-#define HISTORY_SIZE_DEFAULT 1024
+#define HISTORY_SIZE_DEFAULT 4096
 
 /* Calculate the elapsed time from starttime to endtime in milliseconds. */
 #define ELAPSED(starttime, endtime) ((int)(endtime - starttime) / 1000)
@@ -1931,6 +1931,7 @@ static int whip_write_packet(AVFormatContext *s, AVPacket *pkt)
             int ptr = 0;
             while (ptr + 4 <= ret) {
                 uint8_t pt = whip->buf[ptr + 1];
+                uint8_t fmt = (whip->buf[ptr] & 0x1f);
                 /**
                  * Refer to RFC 3550, Section 6.4.1.
                  * The length of this RTCP packet in 32-bit words minus one,
@@ -1939,9 +1940,8 @@ static int whip_write_packet(AVFormatContext *s, AVPacket *pkt)
                 int len = (AV_RB16(&whip->buf[ptr + 2]) + 1) * 4;
                 if (ptr + len > ret) break;
 
-                if (pt == 205) { /* PT=RTPFB */
-                    uint8_t fmt = (whip->buf[ptr] & 0x1f);
-                    if (fmt == 1 && len >= 12) { /* FMT=1 */
+                if (pt == 205 && fmt == 1 && len >= 12) { /* PT=RTPFB, FMT=1 */
+                        int i;
                         /* SRTCP index(4 bytes) + HMAC (SRTP_AES128_CM_SHA1_80 10bytes) */
                         int srtcp_len = len + 4 + 10;
                         int ret = ff_srtp_decrypt(&whip->srtp_recv, whip->buf, &srtcp_len);
@@ -1950,12 +1950,13 @@ static int whip_write_packet(AVFormatContext *s, AVPacket *pkt)
                             // packet is invalid or authentication failed
                             break;
                         }
+                        for (i = 0 ; 14 + i <= len; i = i + 4) {
                         /**
                          *  See https://datatracker.ietf.org/doc/html/rfc4585#section-6.1 
-                         *  TODO: Handle multi NACKs in bundled packet.
+                         *  Handle multi NACKs in bundled packet.
                          */
-                        uint16_t pid = AV_RB16(&whip->buf[ptr + 12]);
-                        uint16_t blp = AV_RB16(&whip->buf[ptr + 14]);
+                        uint16_t pid = AV_RB16(&whip->buf[ptr + 12 + i]);
+                        uint16_t blp = AV_RB16(&whip->buf[ptr + 14 + i]);
 
                         /* retransmit pid + any bit set in blp */
                         for (int bit = -1; bit < 16; bit++) {
@@ -1968,11 +1969,11 @@ static int whip_write_packet(AVFormatContext *s, AVPacket *pkt)
                                 send_rtx_packet(s, it->pkt, it->size);
                                 av_log(whip, AV_LOG_INFO, "WHIP: NACK packet found: size: %d, seq=%d, blp=%d\n", it->size, seq, blp);
                             } else
-                                av_log(whip, AV_LOG_INFO, "WHIP: NACK packet, seq=%d, blp=%d, not found\n", seq, blp);
+                                av_log(whip, AV_LOG_INFO, "WHIP: NACK packet, seq=%d, blp=%d, not found, the latest packet seq: %d\n", seq, blp, whip->history[whip->hist_head-1].seq);
+                        }
                         }
-                    }
                 }
-                ptr += len;
+                break;
             }
 
         }
@@ -2079,7 +2080,7 @@ static const AVOption options[] = {
     { "authorization",      "The optional Bearer token for WHIP Authorization",         OFFSET(authorization),      AV_OPT_TYPE_STRING, { .str = NULL },     0,       0, DEC },
     { "cert_file",          "The optional certificate file path for DTLS",              OFFSET(cert_file),          AV_OPT_TYPE_STRING, { .str = NULL },     0,       0, DEC },
     { "key_file",           "The optional private key file path for DTLS",              OFFSET(key_file),           AV_OPT_TYPE_STRING, { .str = NULL },     0,       0, DEC },
-    { "rtx_history",        "Packet history size",                                      OFFSET(history_size),       AV_OPT_TYPE_INT,    { .i64 = HISTORY_SIZE_DEFAULT },      64,   2048,  DEC },
+    { "rtx_history",        "Packet history size",                                      OFFSET(history_size),       AV_OPT_TYPE_INT,    { .i64 = HISTORY_SIZE_DEFAULT },      64,   INT_MAX,  DEC },
     { NULL },
 };