static int sap_read_header(AVFormatContext *s) { struct SAPState *sap = s->priv_data; char host[1024], path[1024], url[1024]; uint8_t recvbuf[RTP_MAX_PACKET_LENGTH]; int port; int ret, i; AVInputFormat* infmt; if (!ff_network_init()) return AVERROR(EIO); av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port, path, sizeof(path), s->filename); if (port < 0) port = 9875; if (!host[0]) { /* Listen for announcements on sap.mcast.net if no host was specified */ av_strlcpy(host, "224.2.127.254", sizeof(host)); } ff_url_join(url, sizeof(url), "udp", NULL, host, port, "?localport=%d", port); ret = ffurl_open(&sap->ann_fd, url, AVIO_FLAG_READ, &s->interrupt_callback, NULL); if (ret) goto fail; while (1) { int addr_type, auth_len; int pos; ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf) - 1); if (ret == AVERROR(EAGAIN)) continue; if (ret < 0) goto fail; recvbuf[ret] = '\0'; /* Null terminate for easier parsing */ if (ret < 8) { av_log(s, AV_LOG_WARNING, "Received too short packet\n"); continue; } if ((recvbuf[0] & 0xe0) != 0x20) { av_log(s, AV_LOG_WARNING, "Unsupported SAP version packet " "received\n"); continue; } if (recvbuf[0] & 0x04) { av_log(s, AV_LOG_WARNING, "Received stream deletion " "announcement\n"); continue; } addr_type = recvbuf[0] & 0x10; auth_len = recvbuf[1]; sap->hash = AV_RB16(&recvbuf[2]); pos = 4; if (addr_type) pos += 16; /* IPv6 */ else pos += 4; /* IPv4 */ pos += auth_len * 4; if (pos + 4 >= ret) { av_log(s, AV_LOG_WARNING, "Received too short packet\n"); continue; } #define MIME "application/sdp" if (strcmp(&recvbuf[pos], MIME) == 0) { pos += strlen(MIME) + 1; } else if (strncmp(&recvbuf[pos], "v=0\r\n", 5) == 0) { // Direct SDP without a mime type } else { av_log(s, AV_LOG_WARNING, "Unsupported mime type %s\n", &recvbuf[pos]); continue; } sap->sdp = av_strdup(&recvbuf[pos]); break; } av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sap->sdp); ffio_init_context(&sap->sdp_pb, sap->sdp, strlen(sap->sdp), 0, NULL, NULL, NULL, NULL); infmt = av_find_input_format("sdp"); if (!infmt) goto fail; sap->sdp_ctx = avformat_alloc_context(); if (!sap->sdp_ctx) { ret = AVERROR(ENOMEM); goto fail; } sap->sdp_ctx->max_delay = s->max_delay; sap->sdp_ctx->pb = &sap->sdp_pb; sap->sdp_ctx->interrupt_callback = s->interrupt_callback; av_assert0(!sap->sdp_ctx->codec_whitelist && !sap->sdp_ctx->format_whitelist); sap->sdp_ctx-> codec_whitelist = av_strdup(s->codec_whitelist); sap->sdp_ctx->format_whitelist = av_strdup(s->format_whitelist); ret = avformat_open_input(&sap->sdp_ctx, "temp.sdp", infmt, NULL); if (ret < 0) goto fail; if (sap->sdp_ctx->ctx_flags & AVFMTCTX_NOHEADER) s->ctx_flags |= AVFMTCTX_NOHEADER; for (i = 0; i < sap->sdp_ctx->nb_streams; i++) { AVStream *st = avformat_new_stream(s, NULL); if (!st) { ret = AVERROR(ENOMEM); goto fail; } st->id = i; avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec); st->time_base = sap->sdp_ctx->streams[i]->time_base; } return 0; fail: sap_read_close(s); return ret; }