FFmpeg转码实例（摘自FFmpeg示例）

最新推荐文章于 2024-07-19 17:51:57 发布

try_zp_catch

最新推荐文章于 2024-07-19 17:51:57 发布

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本文链接：https://blog.youkuaiyun.com/try_zp_catch/article/details/120264292

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该博客详细介绍了如何使用FFmpeg库将.mp4文件转换为.flv格式。首先打开输入文件，然后找到输入流信息，创建输出上下文，并复制编码参数。接着，分配并初始化流映射，打开输出文件并写入头信息。最后，读取输入帧，重新调整时间戳，写入输出帧，直至文件结束，完成转码过程。

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const char *in_filename = "/sdcard/wang.mp4";
    const char *out_filename = "/sdcard/wang.flv";
    AVOutputFormat *ofmt = NULL;
    AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
    AVPacket pkt;
    int ret, i;
    int stream_index = 0;
    int *stream_mapping = NULL;
    int stream_mapping_size = 0;

    if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
        LOGE("Could not open input file '%s'", in_filename);
        goto end;
    }

    if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
        LOGE("Failed to retrieve input stream information");
        goto end;
    }

    av_dump_format(ifmt_ctx, 0, in_filename, 0);

    avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
    if (!ofmt_ctx) {
        LOGE("Could not create output context\n");
        ret = AVERROR_UNKNOWN;
        goto end;
    }

    stream_mapping_size = ifmt_ctx->nb_streams;
    stream_mapping = static_cast<int *>(av_mallocz_array(stream_mapping_size,
                                                         sizeof(*stream_mapping)));
    if (!stream_mapping) {
        ret = AVERROR(ENOMEM);
        goto end;
    }

    ofmt = ofmt_ctx->oformat;

    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        AVStream *out_stream;
        AVStream *in_stream = ifmt_ctx->streams[i];
        AVCodecParameters *in_codecpar = in_stream->codecpar;

        if (in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO &&
            in_codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
            in_codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
            stream_mapping[i] = -1;
            continue;
        }

        stream_mapping[i] = stream_index++;

        out_stream = avformat_new_stream(ofmt_ctx, NULL);
        if (!out_stream) {
            LOGE("Failed allocating output stream\n");
            ret = AVERROR_UNKNOWN;
            goto end;
        }

        ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
        if (ret < 0) {
            LOGE("Failed to copy codec parameters\n");
            goto end;
        }
        out_stream->codecpar->codec_tag = 0;
    }
    av_dump_format(ofmt_ctx, 0, out_filename, 1);

    if (!(ofmt->flags & AVFMT_NOFILE)) {
        ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
        if (ret < 0) {
            LOGE("Could not open output file '%s'", out_filename);
            goto end;
        }
    }

    ret = avformat_write_header(ofmt_ctx, NULL);
    if (ret < 0) {
        LOGE("Error occurred when opening output file\n");
        goto end;
    }

    while (1) {
        AVStream *in_stream, *out_stream;

        ret = av_read_frame(ifmt_ctx, &pkt);
        if (ret < 0)
            break;

        in_stream  = ifmt_ctx->streams[pkt.stream_index];
        if (pkt.stream_index >= stream_mapping_size ||
            stream_mapping[pkt.stream_index] < 0) {
            av_packet_unref(&pkt);
            continue;
        }

        pkt.stream_index = stream_mapping[pkt.stream_index];
        out_stream = ofmt_ctx->streams[pkt.stream_index];
        log_packet(ifmt_ctx, &pkt, "in");

        /* copy packet */
        pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base,
                                   static_cast<AVRounding>(AV_ROUND_NEAR_INF |
                                                           AV_ROUND_PASS_MINMAX));
        pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base,
                                   static_cast<AVRounding>(AV_ROUND_NEAR_INF |
                                                           AV_ROUND_PASS_MINMAX));
        pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
        pkt.pos = -1;
        log_packet(ofmt_ctx, &pkt, "out");

        ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
        if (ret < 0) {
            LOGE("Error muxing packet\n");
            break;
        }
        av_packet_unref(&pkt);
    }

    av_write_trailer(ofmt_ctx);
    end:

    avformat_close_input(&ifmt_ctx);

    /* close output */
    if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
        avio_closep(&ofmt_ctx->pb);
    avformat_free_context(ofmt_ctx);

    av_freep(&stream_mapping);

    if (ret < 0 && ret != AVERROR_EOF) {
        LOGE("Error occurred: %s\n", av_err2str(ret));
        return ;
    }

    LOGE("转码完成");