为什么ffmpeg示例程序decode_encoding的h264输出文件无法在Quicktime中播放？

Question

我已经使用--enable-gpl --enable-libx264下载并构建了ffmpeg 3.2，并且还构建了示例。

然后我用h264参数运行decode_encoding程序，生成文件test.h264。

然后我无法在Quicktime Player（macOS 10.11.5上的10.4版）中播放此文件。它在VLC中运行良好。

我不明白为什么它不起作用。 ffmpeg documentation表示：

  

QuickTime仅支持YUV平面色彩空间，对于H.264视频，使用4：2：0色度子采样（使用-vf格式= yuv420p或-pix_fmt yuv420p）。

使用ffprobe查看该文件显示它采用的是yuv420p格式：

Input #0, h264, from 'test.h264':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: h264 (High), yuv420p(progressive), 352x288, 25 fps,
    25 tbr, 1200k tbn, 50 tbc

为什么此文件无法在Quicktime中播放。 decode_encoding需要进行哪些调整才能播放？

感谢您的帮助

Answer 1

Quicktime不支持原始基本流。您必须将es放入容器（如mp4）中。 ffmpeg -i test.h.264 -codec copy test.mp4

Answer 2

关于“decode_encoding需要进行哪些调整以使其播放？”的问题：我通过方法video_encode_with_container_example()扩展了ffmpeg / doc / examples中的decoding_encoding示例，以便它写入mp4容器文件一个h264视频流。使用ffmpeg 3.2和x264编译下面的代码，然后调用decoding_encoding mp4。这将生成一个在Quicktime中打开的文件test.mp4。

/*
 * Copyright (c) 2001 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/**
 * @file
 * libavcodec API use example.
 *
 * Note that libavcodec only handles codecs (mpeg, mpeg4, etc...),
 * not file formats (avi, vob, mp4, mov, mkv, mxf, flv, mpegts, mpegps, etc...). See library 'libavformat' for the
 * format handling
 */

#include <math.h>

#include <libavutil/opt.h>
#include <libavcodec/avcodec.h>
//#include <libavutil/audioconvert.h>
#include <libavutil/common.h>
#include <libavutil/imgutils.h>
#include <libavutil/mathematics.h>
#include <libavutil/samplefmt.h>

#include "libavformat/avformat.h"


#define INBUF_SIZE 4096
#define AUDIO_INBUF_SIZE 20480
#define AUDIO_REFILL_THRESH 4096

/* check that a given sample format is supported by the encoder */
static int check_sample_fmt(AVCodec *codec, enum AVSampleFormat sample_fmt)
{
    const enum AVSampleFormat *p = codec->sample_fmts;

    while (*p != AV_SAMPLE_FMT_NONE) {
        if (*p == sample_fmt)
            return 1;
        p++;
    }
    return 0;
}

/* just pick the highest supported samplerate */
static int select_sample_rate(AVCodec *codec)
{
    const int *p;
    int best_samplerate = 0;

    if (!codec->supported_samplerates)
        return 44100;

    p = codec->supported_samplerates;
    while (*p) {
        best_samplerate = FFMAX(*p, best_samplerate);
        p++;
    }
    return best_samplerate;
}

/* select layout with the highest channel count */
static int select_channel_layout(AVCodec *codec)
{
    const uint64_t *p;
    uint64_t best_ch_layout = 0;
    int best_nb_channells   = 0;

    if (!codec->channel_layouts)
        return AV_CH_LAYOUT_STEREO;

    p = codec->channel_layouts;
    while (*p) {
        int nb_channels = av_get_channel_layout_nb_channels(*p);

        if (nb_channels > best_nb_channells) {
            best_ch_layout    = *p;
            best_nb_channells = nb_channels;
        }
        p++;
    }
    return best_ch_layout;
}

/*
 * Audio encoding example
 */
static void audio_encode_example(const char *filename)
{
    AVCodec *codec;
    AVCodecContext *c= NULL;
    AVFrame *frame;
    AVPacket pkt;
    int i, j, k, ret, got_output;
    int buffer_size;
    FILE *f;
    uint16_t *samples;
    float t, tincr;

    printf("Encode audio file %s\n", filename);

    /* find the MP2 encoder */
    codec = avcodec_find_encoder(AV_CODEC_ID_MP2);
    if (!codec) {
        fprintf(stderr, "Codec not found\n");
        exit(1);
    }

    c = avcodec_alloc_context3(codec);

    /* put sample parameters */
    c->bit_rate = 64000;

    /* check that the encoder supports s16 pcm input */
    c->sample_fmt = AV_SAMPLE_FMT_S16;
    if (!check_sample_fmt(codec, c->sample_fmt)) {
        fprintf(stderr, "Encoder does not support sample format %s",
                av_get_sample_fmt_name(c->sample_fmt));
        exit(1);
    }

    /* select other audio parameters supported by the encoder */
    c->sample_rate    = select_sample_rate(codec);
    c->channel_layout = select_channel_layout(codec);
    c->channels       = av_get_channel_layout_nb_channels(c->channel_layout);

    /* open it */
    if (avcodec_open2(c, codec, NULL) < 0) {
        fprintf(stderr, "Could not open codec\n");
        exit(1);
    }

    f = fopen(filename, "wb");
    if (!f) {
        fprintf(stderr, "Could not open %s\n", filename);
        exit(1);
    }

    /* frame containing input raw audio */
    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Could not allocate audio frame\n");
        exit(1);
    }

    frame->nb_samples     = c->frame_size;
    frame->format         = c->sample_fmt;
    frame->channel_layout = c->channel_layout;

    /* the codec gives us the frame size, in samples,
     * we calculate the size of the samples buffer in bytes */
    buffer_size = av_samples_get_buffer_size(NULL, c->channels, c->frame_size,
                                             c->sample_fmt, 0);
    samples = av_malloc(buffer_size);
    if (!samples) {
        fprintf(stderr, "Could not allocate %d bytes for samples buffer\n",
                buffer_size);
        exit(1);
    }
    /* setup the data pointers in the AVFrame */
    ret = avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
                                   (const uint8_t*)samples, buffer_size, 0);
    if (ret < 0) {
        fprintf(stderr, "Could not setup audio frame\n");
        exit(1);
    }

    /* encode a single tone sound */
    t = 0;
    tincr = 2 * M_PI * 440.0 / c->sample_rate;
    for(i=0;i<200;i++) {
        av_init_packet(&pkt);
        pkt.data = NULL; // packet data will be allocated by the encoder
        pkt.size = 0;

        for (j = 0; j < c->frame_size; j++) {
            samples[2*j] = (int)(sin(t) * 10000);

            for (k = 1; k < c->channels; k++)
                samples[2*j + k] = samples[2*j];
            t += tincr;
        }
        /* encode the samples */
        ret = avcodec_encode_audio2(c, &pkt, frame, &got_output);
        if (ret < 0) {
            fprintf(stderr, "Error encoding audio frame\n");
            exit(1);
        }
        if (got_output) {
            fwrite(pkt.data, 1, pkt.size, f);
            av_free_packet(&pkt);
        }
    }

    /* get the delayed frames */
    for (got_output = 1; got_output; i++) {
        ret = avcodec_encode_audio2(c, &pkt, NULL, &got_output);
        if (ret < 0) {
            fprintf(stderr, "Error encoding frame\n");
            exit(1);
        }

        if (got_output) {
            fwrite(pkt.data, 1, pkt.size, f);
            av_free_packet(&pkt);
        }
    }
    fclose(f);

    av_freep(&samples);
    av_frame_free(&frame);
    avcodec_close(c);
    av_free(c);
}

/*
 * Audio decoding.
 */
static void audio_decode_example(const char *outfilename, const char *filename)
{
    AVCodec *codec;
    AVCodecContext *c= NULL;
    int len;
    FILE *f, *outfile;
    uint8_t inbuf[AUDIO_INBUF_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
    AVPacket avpkt;
    AVFrame *decoded_frame = NULL;

    av_init_packet(&avpkt);

    printf("Decode audio file %s to %s\n", filename, outfilename);

    /* find the mpeg audio decoder */
    codec = avcodec_find_decoder(AV_CODEC_ID_MP2);
    if (!codec) {
        fprintf(stderr, "Codec not found\n");
        exit(1);
    }

    c = avcodec_alloc_context3(codec);

    /* open it */
    if (avcodec_open2(c, codec, NULL) < 0) {
        fprintf(stderr, "Could not open codec\n");
        exit(1);
    }

    f = fopen(filename, "rb");
    if (!f) {
        fprintf(stderr, "Could not open %s\n", filename);
        exit(1);
    }
    outfile = fopen(outfilename, "wb");
    if (!outfile) {
        av_free(c);
        exit(1);
    }

    /* decode until eof */
    avpkt.data = inbuf;
    avpkt.size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);

    while (avpkt.size > 0) {
        int got_frame = 0;

        if (!decoded_frame) {
            if (!(decoded_frame = av_frame_alloc())) {
                fprintf(stderr, "Could not allocate audio frame\n");
                exit(1);
            }
        } else {
            //avcodec_get_frame_defaults(decoded_frame);
        }

        len = avcodec_decode_audio4(c, decoded_frame, &got_frame, &avpkt);
        if (len < 0) {
            fprintf(stderr, "Error while decoding\n");
            exit(1);
        }
        if (got_frame) {
            /* if a frame has been decoded, output it */
            int data_size = av_samples_get_buffer_size(NULL, c->channels,
                                                       decoded_frame->nb_samples,
                                                       c->sample_fmt, 1);
            fwrite(decoded_frame->data[0], 1, data_size, outfile);
        }
        avpkt.size -= len;
        avpkt.data += len;
        avpkt.dts =
        avpkt.pts = AV_NOPTS_VALUE;
        if (avpkt.size < AUDIO_REFILL_THRESH) {
            /* Refill the input buffer, to avoid trying to decode
             * incomplete frames. Instead of this, one could also use
             * a parser, or use a proper container format through
             * libavformat. */
            memmove(inbuf, avpkt.data, avpkt.size);
            avpkt.data = inbuf;
            len = fread(avpkt.data + avpkt.size, 1,
                        AUDIO_INBUF_SIZE - avpkt.size, f);
            if (len > 0)
                avpkt.size += len;
        }
    }

    fclose(outfile);
    fclose(f);

    avcodec_close(c);
    av_free(c);
    av_frame_free(&decoded_frame);
}

/*
 * Video encoding in a container example
 */
static void video_encode_with_container_example(const char *filename, int codec_id)
{
    av_register_all();
    avformat_network_init();

    AVOutputFormat* output_format = 0;
    AVFormatContext* format_context = 0;
    AVStream* stream = 0;

    output_format = av_guess_format(0, filename, 0);

    format_context = avformat_alloc_context();
    if (!format_context) {
        printf("could not alloc format_context\n");
        exit(1);
    }

    format_context->oformat = output_format;
    output_format->video_codec = codec_id;

    AVCodec* codec = avcodec_find_encoder(codec_id);

    stream = avformat_new_stream(format_context, codec);
    if (!stream) {
        printf("could not create stream\n");
        avformat_free_context(format_context);
        exit(1);
    }

    AVCodecContext * codec_context = stream->codec;
    stream->time_base = (AVRational){1,25};

    /* put sample parameters */
    codec_context->width = 352;
    codec_context->height = 288;
    codec_context->time_base = stream->time_base;
    codec_context->pix_fmt = AV_PIX_FMT_YUV420P;

    if (format_context->oformat->flags & AVFMT_GLOBALHEADER) {
        codec_context->flags |= CODEC_FLAG_GLOBAL_HEADER;
    }

    codec_context->qmin = 18;
    codec_context->qmax = 18;

    if (avcodec_open2(codec_context, codec, 0) < 0) {
        printf("Could not initialize codec_context\n");
        avcodec_close(stream->codec);
        avformat_free_context(format_context);
        exit(1);
    }

    if (!(output_format->flags & AVFMT_NOFILE)) {
        if (avio_open(&format_context->pb, filename, AVIO_FLAG_READ_WRITE) < 0) {
          printf("could not open stream\n");
          avcodec_close(stream->codec);
          avformat_free_context(format_context);
          exit(1);
        }
    }

    if (avformat_write_header(format_context, 0) < 0) {
        printf("Could not write header\n");
        avcodec_close(stream->codec);
        avformat_free_context(format_context);
        exit(1);
    }

    AVCodecContext *c = stream->codec;
    int i, ret, x, y, got_output;
    AVFrame *frame;
    AVPacket pkt;

    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Could not allocate video frame\n");
        exit(1);
    }
    frame->format = c->pix_fmt;
    frame->width  = c->width;
    frame->height = c->height;

    /* the image can be allocated by any means and av_image_alloc() is
     * just the most convenient way if av_malloc() is to be used */
    ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,
                         c->pix_fmt, 32);
    if (ret < 0) {
        fprintf(stderr, "Could not allocate raw picture buffer\n");
        avcodec_close(stream->codec);
        avformat_free_context(format_context);
        exit(1);
    }

    /* encode 1 second of video */
    for(i = 0; i < 25; i++) {
        av_init_packet(&pkt);
        pkt.data = NULL;    // packet data will be allocated by the encoder
        pkt.size = 0;

        fflush(stdout);
        //printf("prepare frame %i\n", i);
        /* prepare a dummy image */
        /* Y */
        for(y=0;y<c->height;y++) {
            for(x=0;x<c->width;x++) {
                frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
            }
        }

        /* Cb and Cr */
        for(y=0;y<c->height/2;y++) {
            for(x=0;x<c->width/2;x++) {
                frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
                frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
            }
        }
        /* adjust pts if time_base has been modified */
        frame->pts = av_rescale_q(i, stream->codec->time_base, stream->time_base);

        /* encode the image */
        ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
        if (ret < 0) {
            fprintf(stderr, "Error encoding frame\n");
            avcodec_close(stream->codec);
            avformat_free_context(format_context);
            exit(1);
        }

        if (got_output) {
            printf("Write frame %3d, pkt.pts: %i (size=%5d)\n", i, pkt.pts, pkt.size);

            ret = av_interleaved_write_frame(format_context, &pkt);
            if (ret < 0) {
              printf("could not interleaved write frame %d \n", i);
            }
            av_free_packet(&pkt);
        }
    }


    /* get the delayed frames */
    for (got_output = 1; got_output; i++) {
        fflush(stdout);

        ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
        if (ret < 0) {
            fprintf(stderr, "Error encoding frame\n");
            avcodec_close(stream->codec);
            avformat_free_context(format_context);
            exit(1);
        }

        if (got_output) {
            printf("Write frame %3d, pkt.pts: %i (size=%5d)\n", i, pkt.pts, pkt.size);
            ret = av_interleaved_write_frame(format_context, &pkt);
            if (ret < 0) {
                printf("could not interleaved write frame %d \n", i);
            }
            av_free_packet(&pkt);
        }
    }

    av_write_trailer(format_context);

    avcodec_close(stream->codec);

    av_free(c);
    av_freep(&frame->data[0]);
    av_frame_free(&frame);

    if (!(output_format->flags & AVFMT_NOFILE)) {
        avio_close(format_context->pb);
    }

    av_free(format_context);
}


/*
 * Video encoding example
 */
static void video_encode_example(const char *filename, int codec_id)
{
    AVCodec *codec;
    AVCodecContext *c= NULL;
    int i, ret, x, y, got_output;
    FILE *f;
    AVFrame *frame;
    AVPacket pkt;
    uint8_t endcode[] = { 0, 0, 1, 0xb7 };

    printf("Encode video file %s\n", filename);

    // find the mpeg1 video encoder 
    codec = avcodec_find_encoder(codec_id);
    if (!codec) {
        fprintf(stderr, "Codec not found\n");
        exit(1);
    }

    c = avcodec_alloc_context3(codec);

    // put sample parameters 
    c->bit_rate = 400000;
    // resolution must be a multiple of two 
    c->width = 352;
    c->height = 288;
    // frames per second 
    c->time_base= (AVRational){1,25};
    c->gop_size = 10; // emit one intra frame every ten frames 
    c->max_b_frames=1;
    c->pix_fmt = AV_PIX_FMT_YUV420P;

    if(codec_id == AV_CODEC_ID_H264)
        av_opt_set(c->priv_data, "preset", "slow", 0);

    // open it
    if (avcodec_open2(c, codec, NULL) < 0) {
        fprintf(stderr, "Could not open codec\n");
        exit(1);
    }

    f = fopen(filename, "wb");
    if (!f) {
        fprintf(stderr, "Could not open %s\n", filename);
        exit(1);
    }

    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Could not allocate video frame\n");
        exit(1);
    }
    frame->format = c->pix_fmt;
    frame->width  = c->width;
    frame->height = c->height;

    // the image can be allocated by any means and av_image_alloc() is
    // just the most convenient way if av_malloc() is to be used
    ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,
                         c->pix_fmt, 32);
    if (ret < 0) {
        fprintf(stderr, "Could not allocate raw picture buffer\n");
        exit(1);
    }

    // encode 1 second of video
    for(i=0;i<25;i++) {
        av_init_packet(&pkt);
        pkt.data = NULL;    // packet data will be allocated by the encoder
        pkt.size = 0;

        fflush(stdout);
        // prepare a dummy image
        // Y
        for(y=0;y<c->height;y++) {
            for(x=0;x<c->width;x++) {
                frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
            }
        }

        // Cb and Cr
        for(y=0;y<c->height/2;y++) {
            for(x=0;x<c->width/2;x++) {
                frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
                frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
            }
        }

        frame->pts = i;

        // encode the image
        ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
        if (ret < 0) {
            fprintf(stderr, "Error encoding frame\n");
            exit(1);
        }

        if (got_output) {
            printf("Write frame %3d (size=%5d)\n", i, pkt.size);
            fwrite(pkt.data, 1, pkt.size, f);
            av_free_packet(&pkt);
        }
    }

    // get the delayed frames
    for (got_output = 1; got_output; i++) {
        fflush(stdout);

        ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
        if (ret < 0) {
            fprintf(stderr, "Error encoding frame\n");
            exit(1);
        }

        if (got_output) {
            printf("Write frame %3d (size=%5d)\n", i, pkt.size);
            fwrite(pkt.data, 1, pkt.size, f);
            av_free_packet(&pkt);
        }
    }

    // add sequence end code to have a real mpeg file
    fwrite(endcode, 1, sizeof(endcode), f);
    fclose(f);

    avcodec_close(c);
    av_free(c);
    av_freep(&frame->data[0]);
    av_frame_free(&frame);
    printf("\n");
}

/*
 * Video decoding example
 */

static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
                     char *filename)
{
    FILE *f;
    int i;

    f=fopen(filename,"w");
    fprintf(f,"P5\n%d %d\n%d\n",xsize,ysize,255);
    for(i=0;i<ysize;i++)
        fwrite(buf + i * wrap,1,xsize,f);
    fclose(f);
}

static void video_decode_example(const char *outfilename, const char *filename)
{
    AVCodec *codec;
    AVCodecContext *c= NULL;
    int frame, got_picture, len;
    FILE *f;
    AVFrame *picture;
    uint8_t inbuf[INBUF_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
    char buf[1024];
    AVPacket avpkt;

    av_init_packet(&avpkt);

    /* set end of buffer to 0 (this ensures that no overreading happens for damaged mpeg streams) */
    memset(inbuf + INBUF_SIZE, 0, FF_INPUT_BUFFER_PADDING_SIZE);

    printf("Decode video file %s to %s\n", filename, outfilename);

    /* find the mpeg1 video decoder */
    codec = avcodec_find_decoder(AV_CODEC_ID_MPEG1VIDEO);
    if (!codec) {
        fprintf(stderr, "Codec not found\n");
        exit(1);
    }

    c = avcodec_alloc_context3(codec);
    if(codec->capabilities&CODEC_CAP_TRUNCATED)
        c->flags|= CODEC_FLAG_TRUNCATED; /* we do not send complete frames */

    /* For some codecs, such as msmpeg4 and mpeg4, width and height
       MUST be initialized there because this information is not
       available in the bitstream. */

    /* open it */
    if (avcodec_open2(c, codec, NULL) < 0) {
        fprintf(stderr, "Could not open codec\n");
        exit(1);
    }

    /* the codec gives us the frame size, in samples */

    f = fopen(filename, "rb");
    if (!f) {
        fprintf(stderr, "Could not open %s\n", filename);
        exit(1);
    }

    picture = av_frame_alloc();
    if (!picture) {
        fprintf(stderr, "Could not allocate video frame\n");
        exit(1);
    }

    frame = 0;
    for(;;) {
        avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);
        if (avpkt.size == 0)
            break;

        /* NOTE1: some codecs are stream based (mpegvideo, mpegaudio)
           and this is the only method to use them because you cannot
           know the compressed data size before analysing it.

           BUT some other codecs (msmpeg4, mpeg4) are inherently frame
           based, so you must call them with all the data for one
           frame exactly. You must also initialize 'width' and
           'height' before initializing them. */

        /* NOTE2: some codecs allow the raw parameters (frame size,
           sample rate) to be changed at any frame. We handle this, so
           you should also take care of it */

        /* here, we use a stream based decoder (mpeg1video), so we
           feed decoder and see if it could decode a frame */
        avpkt.data = inbuf;
        while (avpkt.size > 0) {
            len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
            if (len < 0) {
                fprintf(stderr, "Error while decoding frame %d\n", frame);
                exit(1);
            }
            if (got_picture) {
                printf("Saving frame %3d\n", frame);
                fflush(stdout);

                /* the picture is allocated by the decoder. no need to
                   free it */
                snprintf(buf, sizeof(buf), outfilename, frame);
                pgm_save(picture->data[0], picture->linesize[0],
                         c->width, c->height, buf);
                frame++;
            }
            avpkt.size -= len;
            avpkt.data += len;
        }
    }

    /* some codecs, such as MPEG, transmit the I and P frame with a
       latency of one frame. You must do the following to have a
       chance to get the last frame of the video */
    avpkt.data = NULL;
    avpkt.size = 0;
    len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
    if (got_picture) {
        printf("Saving last frame %3d\n", frame);
        fflush(stdout);

        /* the picture is allocated by the decoder. no need to
           free it */
        snprintf(buf, sizeof(buf), outfilename, frame);
        pgm_save(picture->data[0], picture->linesize[0],
                 c->width, c->height, buf);
        frame++;
    }

    fclose(f);

    avcodec_close(c);
    av_free(c);
    av_frame_free(&picture);
    printf("\n");
}

int main(int argc, char **argv)
{
    const char *output_type;

    /* register all the codecs */
    avcodec_register_all();

    if (argc < 2) {
        printf("usage: %s output_type\n"
               "API example program to decode/encode a media stream with libavcodec.\n"
               "This program generates a synthetic stream and encodes it to a file\n"
               "named test.h264, test.mp2, test.mpg or test.mp4 depending on output_type.\n"
               "The encoded stream is then decoded and written to a raw data output\n."
               "output_type must be choosen between 'h264', 'mp2', 'mpg', 'mp4'\n",
               argv[0]);
        return 1;
    }
    output_type = argv[1];

    if (!strcmp(output_type, "h264")) {
        video_encode_example("test.h264", AV_CODEC_ID_H264);
    } else if (!strcmp(output_type, "mp4")) {
        video_encode_with_container_example("test.mp4", AV_CODEC_ID_H264);
    } else if (!strcmp(output_type, "mp2")) {
        audio_encode_example("test.mp2");
        audio_decode_example("test.sw", "test.mp2");
    } else if (!strcmp(output_type, "mpg")) {
        video_encode_example("test.mpg", AV_CODEC_ID_MPEG1VIDEO);
        video_decode_example("test%02d.pgm", "test.mpg");
    } else {
        fprintf(stderr, "Invalid output type '%s', choose between 'h264', 'mp2', 'mpg', or 'mp4'\n",
                output_type);
        return 1;
    }

    return 0;
}