ffmepg c语言 dav转mp4 vs代码

你可以使用FFmpeg库来将DAV视频文件转换为MP4格式。以下是一个简单的C语言程序，使用FFmpeg实现此功能：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/imgutils.h>
#include <libavutil/opt.h>
#include <libswscale/swscale.h>

int main(int argc, char *argv[]) {
    AVFormatContext *input_ctx = NULL, *output_ctx = NULL;
    AVCodecContext *decoder_ctx = NULL, *encoder_ctx = NULL;
    AVCodec *decoder = NULL, *encoder = NULL;
    AVFrame *frame = NULL, *tmp_frame = NULL;
    AVPacket *pkt = NULL;
    int ret = 0, video_stream_index = -1, len = 0;
    char *input_file = NULL, *output_file = NULL;

    if (argc != 3) {
        fprintf(stderr, "Usage: %s <input_file> <output_file>\n", argv[0]);
        exit(1);
    }

    input_file = argv[1];
    output_file = argv[2];

    // open input file
    if ((ret = avformat_open_input(&input_ctx, input_file, NULL, NULL)) < 0) {
        fprintf(stderr, "Failed to open input file: %s\n", av_err2str(ret));
        goto end;
    }

    // retrieve stream information
    if ((ret = avformat_find_stream_info(input_ctx, NULL)) < 0) {
        fprintf(stderr, "Failed to retrieve input stream information: %s\n", av_err2str(ret));
        goto end;
    }

    // find video stream
    for (int i = 0; i < input_ctx->nb_streams; i++) {
        if (input_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream_index = i;
            break;
        }
    }

    if (video_stream_index == -1) {
        fprintf(stderr, "Failed to find video stream\n");
        goto end;
    }

    // allocate decoder context
    decoder = avcodec_find_decoder(input_ctx->streams[video_stream_index]->codecpar->codec_id);
    if (!decoder) {
        fprintf(stderr, "Failed to find decoder\n");
        goto end;
    }

    decoder_ctx = avcodec_alloc_context3(decoder);
    if (!decoder_ctx) {
        fprintf(stderr, "Failed to allocate decoder context\n");
        goto end;
    }

    // copy codec parameters to decoder context
    if ((ret = avcodec_parameters_to_context(decoder_ctx, input_ctx->streams[video_stream_index]->codecpar)) < 0) {
        fprintf(stderr, "Failed to copy codec parameters to decoder context: %s\n", av_err2str(ret));
        goto end;
    }

    // open decoder
    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
        fprintf(stderr, "Failed to open decoder: %s\n", av_err2str(ret));
        goto end;
    }

    // allocate encoder context
    encoder = avcodec_find_encoder(AV_CODEC_ID_MPEG4);
    if (!encoder) {
        fprintf(stderr, "Failed to find encoder\n");
        goto end;
    }

    encoder_ctx = avcodec_alloc_context3(encoder);
    if (!encoder_ctx) {
        fprintf(stderr, "Failed to allocate encoder context\n");
        goto end;
    }

    // set encoder parameters
    encoder_ctx->bit_rate = 400000;
    encoder_ctx->width = decoder_ctx->width;
    encoder_ctx->height = decoder_ctx->height;
    encoder_ctx->time_base = decoder_ctx->time_base;
    encoder_ctx->framerate = decoder_ctx->framerate;
    encoder_ctx->gop_size = 10;
    encoder_ctx->max_b_frames = 1;
    encoder_ctx->pix_fmt = AV_PIX_FMT_YUV420P;

    // open encoder
    if ((ret = avcodec_open2(encoder_ctx, encoder, NULL)) < 0) {
        fprintf(stderr, "Failed to open encoder: %s\n", av_err2str(ret));
        goto end;
    }

    // allocate frame
    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Failed to allocate frame\n");
        goto end;
    }

    // allocate temporary frame
    tmp_frame = av_frame_alloc();
    if (!tmp_frame) {
        fprintf(stderr, "Failed to allocate temporary frame\n");
        goto end;
    }

    // allocate packet
    pkt = av_packet_alloc();
    if (!pkt) {
        fprintf(stderr, "Failed to allocate packet\n");
        goto end;
    }

    // open output file
    if ((ret = avformat_alloc_output_context2(&output_ctx, NULL, NULL, output_file)) < 0) {
        fprintf(stderr, "Failed to allocate output context: %s\n", av_err2str(ret));
        goto end;
    }

    // add video stream to output context
    AVStream *out_stream = avformat_new_stream(output_ctx, NULL);
    if (!out_stream) {
        fprintf(stderr, "Failed to allocate output stream\n");
        goto end;
    }

    // copy codec parameters from encoder context to output stream
    if ((ret = avcodec_parameters_from_context(out_stream->codecpar, encoder_ctx)) < 0) {
        fprintf(stderr, "Failed to copy codec parameters from encoder context to output stream: %s\n", av_err2str(ret));
        goto end;
    }

    // set time base for output stream
    out_stream->time_base = encoder_ctx->time_base;

    // write header to output file
    if ((ret = avformat_write_header(output_ctx, NULL)) < 0) {
        fprintf(stderr, "Failed to write header to output file: %s\n", av_err2str(ret));
        goto end;
    }

    // read packets from input file, decode them, and encode them to output file
    while (av_read_frame(input_ctx, pkt) >= 0) {
        if (pkt->stream_index != video_stream_index) {
            av_packet_unref(pkt);
            continue;
        }

        // decode packet
        len = avcodec_send_packet(decoder_ctx, pkt);
        if (len < 0) {
            fprintf(stderr, "Failed to decode packet: %s\n", av_err2str(len));
            goto end;
        }

        while (len >= 0) {
            // get decoded frame
            len = avcodec_receive_frame(decoder_ctx, tmp_frame);
            if (len == AVERROR(EAGAIN) || len == AVERROR_EOF) {
                break;
            } else if (len < 0) {
                fprintf(stderr, "Failed to receive decoded frame: %s\n", av_err2str(len));
                goto end;
            }

            // convert frame to output format
            if (tmp_frame->format != encoder_ctx->pix_fmt || tmp_frame->width != encoder_ctx->width || tmp_frame->height != encoder_ctx->height) {
                if (frame) {
                    av_frame_free(&frame);
                }

                frame = av_frame_alloc();
                if (!frame) {
                    fprintf(stderr, "Failed to allocate frame\n");
                    goto end;
                }

                frame->format = encoder_ctx->pix_fmt;
                frame->width = encoder_ctx->width;
                frame->height = encoder_ctx->height;

                if ((ret = av_frame_get_buffer(frame, 32)) < 0) {
                    fprintf(stderr, "Failed to allocate frame buffer: %s\n", av_err2str(ret));
                    goto end;
                }

                // convert frame
                struct SwsContext *sws_ctx = sws_getContext(tmp_frame->width, tmp_frame->height, (enum AVPixelFormat)tmp_frame->format,
                                                            encoder_ctx->width, encoder_ctx->height, encoder_ctx->pix_fmt,
                                                            SWS_BILINEAR, NULL, NULL, NULL);
                if (!sws_ctx) {
                    fprintf(stderr, "Failed to allocate SwsContext\n");
                    goto end;
                }

                sws_scale(sws_ctx, tmp_frame->data, tmp_frame->linesize, 0, tmp_frame->height, frame->data, frame->linesize);
                sws_freeContext(sws_ctx);
            } else {
                frame = tmp_frame;
                tmp_frame = NULL;
            }

            // encode frame
            len = avcodec_send_frame(encoder_ctx, frame);
            if (len < 0) {
                fprintf(stderr, "Failed to encode frame: %s\n", av_err2str(len));
                goto end;
            }

            while (len >= 0) {
                // get encoded packet
                len = avcodec_receive_packet(encoder_ctx, pkt);
                if (len == AVERROR(EAGAIN) || len == AVERROR_EOF) {
                    break;
                } else if (len < 0) {
                    fprintf(stderr, "Failed to receive encoded packet: %s\n", av_err2str(len));
                    goto end;
                }

                // write packet to output file
                if ((ret = av_write_frame(output_ctx, pkt)) < 0) {
                    fprintf(stderr, "Failed to write packet to output file: %s\n", av_err2str(ret));
                    goto end;
                }

                av_packet_unref(pkt);
            }
        }

        av_packet_unref(pkt);
    }

    // flush encoder
    if ((ret = avcodec_send_frame(encoder_ctx, NULL)) < 0) {
        fprintf(stderr, "Failed to flush encoder: %s\n", av_err2str(ret));
        goto end;
    }

    while (ret >= 0) {
        ret = avcodec_receive_packet(encoder_ctx, pkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        } else if (ret < 0) {
            fprintf(stderr, "Failed to receive encoded packet: %s\n", av_err2str(ret));
            goto end;
        }

        // write packet to output file
        if ((ret = av_write_frame(output_ctx, pkt)) < 0) {
            fprintf(stderr, "Failed to write packet to output file: %s\n", av_err2str(ret));
            goto end;
        }

        av_packet_unref(pkt);
    }

    // write trailer to output file
    if ((ret = av_write_trailer(output_ctx)) < 0) {
        fprintf(stderr, "Failed to write trailer to output file: %s\n", av_err2str(ret));
        goto end;
    }

    printf("Finished converting %s to %s\n", input_file, output_file);

end:
    if (input_ctx) {
        avformat_close_input(&input_ctx);
    }

    if (output_ctx) {
        avio_closep(&output_ctx->pb);
        avformat_free_context(output_ctx);
    }

    if (decoder_ctx) {
        avcodec_free_context(&decoder_ctx);
    }

    if (encoder_ctx) {
        avcodec_free_context(&encoder_ctx);
    }

    if (frame) {
        av_frame_free(&frame);
    }

    if (tmp_frame) {
        av_frame_free(&tmp_frame);
    }

    if (pkt) {
        av_packet_free(&pkt);
    }

    return ret < 0;
}

此程序使用了FFmpeg的AVFormatContext、AVCodecContext、AVCodec、AVFrame、AVPacket和SwsContext等结构体/函数。使用VS Code编写C代码时，需要配置好FFmpeg的库文件和头文件路径。可以在VS Code的tasks.json文件中添加以下代码：

{
    "label": "build",
    "type": "shell",
    "command": "gcc",
    "args": [
        "-g",
        "-o",
        "${fileDirname}\\${fileBasenameNoExtension}.exe",
        "${file}",
        "-lavcodec",
        "-lavformat",
        "-lavutil",
        "-lswscale",
        "-lmingw32",
        "-lSDL2main",
        "-lSDL2",
        "-I${workspaceFolder}\\include",
        "-L${workspaceFolder}\\lib",
        "-Wl,-Bstatic",
        "-lstdc++",
        "-lpng",
        "-lz",
        "-lm",
        "-Wl,-Bdynamic",
        "-lwinmm",
        "-lole32",
        "-loleaut32",
        "-luuid",
        "-lcomctl32",
        "-lcomdlg32"
    ],
    "options": {
        "cwd": "${workspaceFolder}"
    },
    "problemMatcher": {
        "owner": "cpp",
        "fileLocation": ["relative", "${workspaceFolder}"],
        "pattern": {
            "regexp": "^(.*):(\\\\d+):(\\\\d+):\\s+(warning|error):\\s+(.*)$",
            "file": 1,
            "line": 2,
            "column": 3,
            "severity": 4,
            "message": 5
        }
    }
}

此处假设你的FFmpeg库文件和头文件保存在VS Code工作区的lib和include文件夹中。你需要根据实际情况修改这些路径。然后，你可以使用Ctrl+Shift+B命令来编译和运行程序。