前面的博文中已经交代过，ffmpeg打开视频慢主要是因为av_find_stream_info 耗时久。下面给出重写查找音视频stream info的一段代码，用来替代av_find_stream_info 。
static int try_decode_frame(AVFormatContext *s, AVStream *st, AVPacket *avpkt, AVDictionary **options) { const AVCodec *codec; int got_picture = 1, ret = 0; AVFrame *frame = av_frame_alloc(); AVSubtitle subtitle; AVPacket pkt = *avpkt; if (!frame) return AVERROR(ENOMEM); if (!avcodec_is_open(st->codec) && st->info->found_decoder <= 0 && (st->codec->codec_id != -st->info->found_decoder || !st->codec->codec_id)) { AVDictionary *thread_opt = NULL; codec = avcodec_find_decoder( st->codec->codec_id); if (!codec) { st->info->found_decoder = -st->codec->codec_id; ret = -1; goto fail; } /* Force thread count to 1 since the H.264 decoder will not extract * SPS and PPS to extradata during multi-threaded decoding. */ av_dict_set(options ? options : &thread_opt, "threads", "1", 0); ret = avcodec_open2(st->codec, codec, options ? options : &thread_opt); if (!options) av_dict_free(&thread_opt); if (ret < 0) { st->info->found_decoder = -st->codec->codec_id; goto fail; } st->info->found_decoder = 1; } else if (!st->info->found_decoder) st->info->found_decoder = 1; if (st->info->found_decoder < 0) { ret = -1; goto fail; } got_picture = 0; switch (st->codec->codec_type) { case AVMEDIA_TYPE_VIDEO: if(st->codec->width > 0 && st->codec->height > 0 && st->codec->pix_fmt != AV_PIX_FMT_NONE) { ret = 0; break; } ret = avcodec_decode_video2(st->codec, frame, &got_picture, &pkt); break; case AVMEDIA_TYPE_AUDIO: ret = avcodec_decode_audio4(st->codec, frame, &got_picture, &pkt); break; case AVMEDIA_TYPE_SUBTITLE: ret = avcodec_decode_subtitle2(st->codec, &subtitle, &got_picture, &pkt); ret = pkt.size; break; default: break; } if (ret >= 0) { if (got_picture) st->nb_decoded_frames++; pkt.data += ret; pkt.size -= ret; ret = got_picture; } if (!pkt.data && !got_picture) ret = -1; fail: av_frame_free(&frame); return ret; } static int ff_alloc_extradata(AVCodecContext *avctx, int size) { int ret; if (size < 0 || size >= INT32_MAX - FF_INPUT_BUFFER_PADDING_SIZE) { avctx->extradata_size = 0; return AVERROR(EINVAL); } avctx->extradata = (uint8_t *)av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE); if (avctx->extradata) { memset(avctx->extradata + size, 0, FF_INPUT_BUFFER_PADDING_SIZE); avctx->extradata_size = size; ret = 0; } else { avctx->extradata_size = 0; ret = AVERROR(ENOMEM); } return ret; } static AVPacket *add_to_pktbuf(AVPacketList **packet_buffer, AVPacket *pkt, AVPacketList **plast_pktl) { AVPacketList *pktl = (AVPacketList *)av_mallocz(sizeof(AVPacketList)); if (!pktl) return NULL; if (*packet_buffer) (*plast_pktl)->next = pktl; else *packet_buffer = pktl; /* Add the packet in the buffered packet list. */ *plast_pktl = pktl; pktl->pkt = *pkt; return &pktl->pkt; } static void free_packet_buffer(AVPacketList **pkt_buf, AVPacketList **pkt_buf_end) { while (*pkt_buf) { AVPacketList *pktl = *pkt_buf; *pkt_buf = pktl->next; av_free_packet(&pktl->pkt); av_freep(&pktl); } *pkt_buf_end = NULL; } static int ff_check_interrupt(AVIOInterruptCB *cb) { int ret; if (cb && cb->callback && (ret = cb->callback(cb->opaque))) return ret; return 0; } static int has_codec_parameters(AVStream *st, const char **errmsg_ptr,bool keypacket = false) { AVCodecContext *avctx = st->codec; #define FAIL(errmsg) do { if (errmsg_ptr) *errmsg_ptr = errmsg; return 0; } while (0) /* if(keypacket) { static int packetCount = 1; packetCount++; if(packetCount > 1) cout << "packetCount too much" <<endl; }*/ switch (avctx->codec_type) { case AVMEDIA_TYPE_AUDIO: if(avctx->codec_id == AV_CODEC_ID_NONE) break; if (st->info->found_decoder >= 0 && avctx->sample_fmt == AV_SAMPLE_FMT_NONE) FAIL("unspecified sample format"); if (!avctx->sample_rate) FAIL("unspecified sample rate"); if (!avctx->channels) FAIL("unspecified number of channels"); if (st->info->found_decoder >= 0 && !st->nb_decoded_frames && avctx->codec_id == AV_CODEC_ID_DTS) FAIL("no decodable DTS frames"); break; case AVMEDIA_TYPE_VIDEO: if (!avctx->width) FAIL("unspecified size"); if (st->info->found_decoder >= 0 && avctx->pix_fmt == AV_PIX_FMT_NONE) FAIL("unspecified pixel format"); break; case AVMEDIA_TYPE_DATA: return 1; case AVMEDIA_TYPE_UNKNOWN: FAIL("unspecified codec type"); break; default: return 0; } return 1; } static const AVCodec *find_decoder(AVFormatContext *s, AVStream *st, enum AVCodecID codec_id) { if (st->codec->codec) return st->codec->codec; switch (st->codec->codec_type) { case AVMEDIA_TYPE_VIDEO: if (s->video_codec) return s->video_codec; break; case AVMEDIA_TYPE_AUDIO: if (s->audio_codec) return s->audio_codec; break; case AVMEDIA_TYPE_SUBTITLE: if (s->subtitle_codec) return s->subtitle_codec; break; } return avcodec_find_decoder(codec_id); } static int alloc_and_copy_exterdata(AVCodecContext *dest, const AVCodecContext *src,size_t size ,size_t pad) { if(src->extradata && size > 0) { dest->extradata = (uint8_t *)av_malloc(size + pad); if(dest->extradata == nullptr) { goto fail; } memcpy(dest->extradata, src->extradata, size); if(pad) { memset((uint8_t *)dest->extradata + size, 0, pad); } } return 0; fail: av_freep(&dest->extradata); return AVERROR(ENOMEM); } static int alloc_and_copy_intra_matrix(AVCodecContext *dest, const AVCodecContext *src,size_t size ,size_t pad) { if(src->intra_matrix && size > 0) { dest->intra_matrix = (uint16_t *)av_malloc(size + pad); if(dest->intra_matrix == nullptr) { goto fail; } memcpy(dest->intra_matrix, src->intra_matrix, size); if(pad) { memset((uint8_t *)dest->intra_matrix + size, 0, pad); } } fail: av_freep(&dest->intra_matrix); return AVERROR(ENOMEM); } static int alloc_and_copy_inter_matrix(AVCodecContext *dest, const AVCodecContext *src,size_t size ,size_t pad) { if(src->inter_matrix && size > 0) { dest->inter_matrix = (uint16_t *)av_malloc(size + pad); if(dest->inter_matrix == nullptr) { goto fail; } memcpy(dest->inter_matrix, src->inter_matrix, size); if(pad) { memset((uint8_t *)dest->inter_matrix + size, 0, pad); } } fail: av_freep(&dest->inter_matrix); return AVERROR(ENOMEM); } static int alloc_and_copy_rc_override(AVCodecContext *dest, const AVCodecContext *src,size_t size ,size_t pad) { if(src->rc_override && size > 0) { dest->rc_override = (RcOverride *)av_malloc(size + pad); if(dest->rc_override == nullptr) { goto fail; } memcpy(dest->rc_override, src->rc_override, size); if(pad) { memset((uint8_t *)dest->rc_override + size, 0, pad); } } fail: av_freep(&dest->rc_override); return AVERROR(ENOMEM); } static int avcodec_copy_context_private(AVCodecContext *dest, const AVCodecContext *src) { if(!src) { return -1; } const AVCodec *orig_codec = dest->codec; uint8_t *orig_priv_data = (uint8_t *)dest->priv_data; if (avcodec_is_open(dest)) { // check that the dest context is uninitialized av_log(dest, AV_LOG_ERROR, "Tried to copy AVCodecContext %p into already-initialized %p ", src, dest); return AVERROR(EINVAL); } av_opt_free(dest); memcpy(dest, src, sizeof(*dest)); dest->priv_data = orig_priv_data; if (orig_priv_data) av_opt_copy(orig_priv_data, src->priv_data); dest->codec = orig_codec; /* set values specific to opened codecs back to their default state */ dest->slice_offset = NULL; dest->hwaccel = NULL; dest->internal = NULL; /* reallocate values that should be allocated separately */ //dest->rc_eq = NULL; dest->extradata = NULL; dest->intra_matrix = NULL; dest->inter_matrix = NULL; dest->rc_override = NULL; dest->subtitle_header = NULL; /* if (src->rc_eq) { dest->rc_eq = av_strdup(src->rc_eq); if (!dest->rc_eq) return AVERROR(ENOMEM); }*/ int ret = 0; ret = alloc_and_copy_exterdata(dest, src, src->extradata_size, FF_INPUT_BUFFER_PADDING_SIZE); if(ret < 0) { return ret ; } ret = alloc_and_copy_intra_matrix(dest, src, 64 * sizeof(int16_t), 0); if(ret < 0) { return ret ; } ret = alloc_and_copy_inter_matrix(dest, src, 64 * sizeof(int16_t), 0); if(ret < 0) { return ret ; } ret = alloc_and_copy_rc_override(dest, src,src->rc_override_count * sizeof(*src->rc_override), 0); return ret ; } static int avformatFindStreamInfo(AVFormatContext *ic, AVDictionary **options,std::vector<shared_ptr<AVPacket>> &packets,int timeout = 5) { int i, count, ret = 0, j; int64_t read_size; AVStream *st; // AVPacket *pkt; AVPacket packet; int64_t old_offset = 0; int64_t last_offset = 0; bool firstKeyPacket = false; int tryCount = 0; int orig_nb_streams = ic->nb_streams; int flush_codecs = ic->probesize > 0; int64_t startTime = av_gettime(); int64_t max_analyze_duration = ic->max_analyze_duration2; for (i = 0; i < ic->nb_streams; i++) { const AVCodec *codec; AVDictionary *thread_opt = NULL; st = ic->streams[i]; if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO || st->codec->codec_type == AVMEDIA_TYPE_SUBTITLE) { if (!st->codec->time_base.num) st->codec->time_base = st->time_base; } if (!st->parser && !(ic->flags & AVFMT_FLAG_NOPARSE)) { st->parser = av_parser_init(st->codec->codec_id); if (st->parser) { if (st->need_parsing == AVSTREAM_PARSE_HEADERS) { st->parser->flags |= PARSER_FLAG_COMPLETE_FRAMES; } else if (st->need_parsing == AVSTREAM_PARSE_FULL_RAW) { st->parser->flags |= PARSER_FLAG_USE_CODEC_TS; } } else if (st->need_parsing) { } } codec = avcodec_find_decoder(st->codec->codec_id); av_dict_set(options ? &options[i] : &thread_opt, "threads", "1", 0); if (!has_codec_parameters(st, NULL) && st->request_probe <= 0) { if (codec && !st->codec->codec) if (avcodec_open2(st->codec, codec, options ? &options[i] : &thread_opt) < 0) av_log(ic, AV_LOG_WARNING, "Failed to open codec in av_find_stream_info "); } if (!options) av_dict_free(&thread_opt); } for (i = 0; i < ic->nb_streams; i++) { ic->streams[i]->info->fps_first_dts = AV_NOPTS_VALUE; ic->streams[i]->info->fps_last_dts = AV_NOPTS_VALUE; } count = 0; read_size = 0; bool saveAudioFlag = false; shared_ptr<AVPacket> lastAudioPacket[AudioPacketsNum] = {nullptr}; for (;;) { if (ff_check_interrupt(&ic->interrupt_callback)) { ret = AVERROR_EXIT; av_log(ic, AV_LOG_DEBUG, "interrupted "); break; } if(av_gettime() - startTime > timeout * 1000 * 1000) { ret = -1; break; } /* check if one codec still needs to be handled */ for (i = 0; i < ic->nb_streams; i++) { st = ic->streams[i]; if (!has_codec_parameters(st, NULL,firstKeyPacket)) break; if (st->parser && st->parser->parser->split && !st->codec->extradata) break; } if (i == ic->nb_streams && ic->nb_streams > 0) { break; } shared_ptr<AVPacket> pkt((AVPacket*)av_malloc(sizeof(AVPacket)), [&](AVPacket *p) { av_free_packet(p); av_freep(&p); }); av_init_packet(pkt.get()); old_offset = avio_tell(ic->pb); ret = av_read_frame(ic, pkt.get()); if (ret == AVERROR(EAGAIN)) { std::this_thread::sleep_for(std::chrono::milliseconds(100)); continue; } if (ret < 0) { /* EOF or error*/ break; } if(ic->nb_streams == 0) return -1; auto codeType = ic->streams[pkt->stream_index]->codec->codec_type; if(codeType == AVMEDIA_TYPE_VIDEO && pkt->flags&AV_PKT_FLAG_KEY) { firstKeyPacket = true; } if(!firstKeyPacket && codeType == AVMEDIA_TYPE_VIDEO) { continue; } shared_ptr<AVPacket> pkt1((AVPacket*)av_malloc(sizeof(AVPacket)), [&](AVPacket *p) { av_free_packet(p); av_freep(&p); }); av_init_packet(pkt1.get()); av_copy_packet(pkt1.get(),pkt.get()); packets.push_back(pkt1); st = ic->streams[pkt->stream_index]; if (!(st->disposition & AV_DISPOSITION_ATTACHED_PIC)) read_size += pkt->size; if (pkt->dts != AV_NOPTS_VALUE && st->codec_info_nb_frames > 1) { /* check for non-increasing dts */ if (st->info->fps_last_dts != AV_NOPTS_VALUE && st->info->fps_last_dts >= pkt->dts) { st->info->fps_first_dts = st->info->fps_last_dts = AV_NOPTS_VALUE; } /* Check for a discontinuity in dts. If the difference in dts * is more than 1000 times the average packet duration in the * sequence, we treat it as a discontinuity. */ if (st->info->fps_last_dts != AV_NOPTS_VALUE && st->info->fps_last_dts_idx > st->info->fps_first_dts_idx && (pkt->dts - st->info->fps_last_dts) / 1000 > (st->info->fps_last_dts - st->info->fps_first_dts) / (st->info->fps_last_dts_idx - st->info->fps_first_dts_idx)) { st->info->fps_first_dts = st->info->fps_last_dts = AV_NOPTS_VALUE; } /* update stored dts values */ if (st->info->fps_first_dts == AV_NOPTS_VALUE) { st->info->fps_first_dts = pkt->dts; st->info->fps_first_dts_idx = st->codec_info_nb_frames; } st->info->fps_last_dts = pkt->dts; st->info->fps_last_dts_idx = st->codec_info_nb_frames; } if (st->parser && st->parser->parser->split && !st->codec->extradata) { int i = st->parser->parser->split(st->codec, pkt->data, pkt->size); if (i > 0 && i < FF_MAX_EXTRADATA_SIZE) { if (ff_alloc_extradata(st->codec, i)) return AVERROR(ENOMEM); memcpy(st->codec->extradata, pkt->data, st->codec->extradata_size); } } auto decodeRet = try_decode_frame(ic, st, pkt.get(), (options && i < orig_nb_streams) ? &options[i] : NULL); st->codec_info_nb_frames++; } for (i = 0; i < ic->nb_streams; i++) { st = ic->streams[i]; avcodec_close(st->codec); } for (i = 0; i < ic->nb_streams; i++) { st = ic->streams[i]; if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) { if (st->codec->codec_id == AV_CODEC_ID_RAWVIDEO && !st->codec->codec_tag && !st->codec->bits_per_coded_sample) { uint32_t tag= avcodec_pix_fmt_to_codec_tag(st->codec->pix_fmt); /* if (avpriv_find_pix_fmt(ff_raw_pix_fmt_tags, tag) == st->codec->pix_fmt) st->codec->codec_tag= tag;*/ } if (!st->r_frame_rate.num) { if ( st->codec->time_base.den * (int64_t) st->time_base.num <= st->codec->time_base.num * st->codec->ticks_per_frame * (int64_t) st->time_base.den) { st->r_frame_rate.num = st->codec->time_base.den; st->r_frame_rate.den = st->codec->time_base.num * st->codec->ticks_per_frame; } else { st->r_frame_rate.num = st->time_base.den; st->r_frame_rate.den = st->time_base.num; } } } else if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO) { if (!st->codec->bits_per_coded_sample) st->codec->bits_per_coded_sample = av_get_bits_per_sample(st->codec->codec_id); // set stream disposition based on audio service type switch (st->codec->audio_service_type) { case AV_AUDIO_SERVICE_TYPE_EFFECTS: st->disposition = AV_DISPOSITION_CLEAN_EFFECTS; break; case AV_AUDIO_SERVICE_TYPE_VISUALLY_IMPAIRED: st->disposition = AV_DISPOSITION_VISUAL_IMPAIRED; break; case AV_AUDIO_SERVICE_TYPE_HEARING_IMPAIRED: st->disposition = AV_DISPOSITION_HEARING_IMPAIRED; break; case AV_AUDIO_SERVICE_TYPE_COMMENTARY: st->disposition = AV_DISPOSITION_COMMENT; break; case AV_AUDIO_SERVICE_TYPE_KARAOKE: st->disposition = AV_DISPOSITION_KARAOKE; break; } } } find_stream_info_err: for (i = 0; i < ic->nb_streams; i++) { st = ic->streams[i]; if (ic->streams[i]->codec->codec_type != AVMEDIA_TYPE_AUDIO) ic->streams[i]->codec->thread_count = 0; if (st->info) av_freep(&st->info->duration_error); av_freep(&ic->streams[i]->info); } if(ic->nb_streams == 0) ret = -1; return ret; }
这段代码的宗旨是找到音视频必要的信息后，立即返回。方法参数里传入vector> packets 是为了保存在查找的过程中已经从context中读取的视频包。如果不保存，这些视频包将会丢掉，同样会增加视频打开的时间。经现场测试，主流的摄像机例如海康，英飞拓，中威等都可以用它来打开。注意：文件不可以用这种方式打开。如果使用这段代码打不开视频或有疑问，请联系我：350197870。
视频下载地址：http://www.chungen90.com/?news_33/
Demo下载地址： http://www.chungen90.com/?news_34