build: Integrate multilibrary examples into the build system

This includes moving libavformat/output-example to doc/examples/output.
2025-06-14 22:15:12 +02:00 · 2013-11-02 17:05:28 +01:00
parent 14abeaa43d
commit ab81f24ad4
5 changed files with 26 additions and 8 deletions
--- a/doc/examples/output.c
+++ b/doc/examples/output.c
@ -0,0 +1,527 @@
+/*
+ * Copyright (c) 2003 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
+ * libavformat API example.
+ *
+ * @example doc/examples/output.c
+ * Output a media file in any supported libavformat format.
+ * The default codecs are used.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+#include "libavutil/mathematics.h"
+#include "libavformat/avformat.h"
+#include "libswscale/swscale.h"
+
+/* 5 seconds stream duration */
+#define STREAM_DURATION   5.0
+#define STREAM_FRAME_RATE 25 /* 25 images/s */
+#define STREAM_NB_FRAMES  ((int)(STREAM_DURATION * STREAM_FRAME_RATE))
+#define STREAM_PIX_FMT    AV_PIX_FMT_YUV420P /* default pix_fmt */
+
+static int sws_flags = SWS_BICUBIC;
+
+/**************************************************************/
+/* audio output */
+
+static float t, tincr, tincr2;
+static int16_t *samples;
+static int audio_input_frame_size;
+
+/*
+ * add an audio output stream
+ */
+static AVStream *add_audio_stream(AVFormatContext *oc, enum AVCodecID codec_id)
+{
+    AVCodecContext *c;
+    AVStream *st;
+    AVCodec *codec;
+
+    /* find the audio encoder */
+    codec = avcodec_find_encoder(codec_id);
+    if (!codec) {
+        fprintf(stderr, "codec not found\n");
+        exit(1);
+    }
+
+    st = avformat_new_stream(oc, codec);
+    if (!st) {
+        fprintf(stderr, "Could not alloc stream\n");
+        exit(1);
+    }
+
+    c = st->codec;
+
+    /* put sample parameters */
+    c->sample_fmt  = AV_SAMPLE_FMT_S16;
+    c->bit_rate    = 64000;
+    c->sample_rate = 44100;
+    c->channels    = 2;
+
+    // some formats want stream headers to be separate
+    if (oc->oformat->flags & AVFMT_GLOBALHEADER)
+        c->flags |= CODEC_FLAG_GLOBAL_HEADER;
+
+    return st;
+}
+
+static void open_audio(AVFormatContext *oc, AVStream *st)
+{
+    AVCodecContext *c;
+
+    c = st->codec;
+
+    /* open it */
+    if (avcodec_open2(c, NULL, NULL) < 0) {
+        fprintf(stderr, "could not open codec\n");
+        exit(1);
+    }
+
+    /* init signal generator */
+    t     = 0;
+    tincr = 2 * M_PI * 110.0 / c->sample_rate;
+    /* increment frequency by 110 Hz per second */
+    tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
+
+    if (c->codec->capabilities & CODEC_CAP_VARIABLE_FRAME_SIZE)
+        audio_input_frame_size = 10000;
+    else
+        audio_input_frame_size = c->frame_size;
+    samples = av_malloc(audio_input_frame_size *
+                        av_get_bytes_per_sample(c->sample_fmt) *
+                        c->channels);
+}
+
+/* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
+ * 'nb_channels' channels. */
+static void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
+{
+    int j, i, v;
+    int16_t *q;
+
+    q = samples;
+    for (j = 0; j < frame_size; j++) {
+        v = (int)(sin(t) * 10000);
+        for (i = 0; i < nb_channels; i++)
+            *q++ = v;
+        t     += tincr;
+        tincr += tincr2;
+    }
+}
+
+static void write_audio_frame(AVFormatContext *oc, AVStream *st)
+{
+    AVCodecContext *c;
+    AVPacket pkt = { 0 }; // data and size must be 0;
+    AVFrame *frame = av_frame_alloc();
+    int got_packet;
+
+    av_init_packet(&pkt);
+    c = st->codec;
+
+    get_audio_frame(samples, audio_input_frame_size, c->channels);
+    frame->nb_samples = audio_input_frame_size;
+    avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
+                             (uint8_t *)samples,
+                             audio_input_frame_size *
+                             av_get_bytes_per_sample(c->sample_fmt) *
+                             c->channels, 1);
+
+    avcodec_encode_audio2(c, &pkt, frame, &got_packet);
+    if (!got_packet)
+        return;
+
+    pkt.stream_index = st->index;
+
+    /* Write the compressed frame to the media file. */
+    if (av_interleaved_write_frame(oc, &pkt) != 0) {
+        fprintf(stderr, "Error while writing audio frame\n");
+        exit(1);
+    }
+    avcodec_free_frame(&frame);
+}
+
+static void close_audio(AVFormatContext *oc, AVStream *st)
+{
+    avcodec_close(st->codec);
+
+    av_free(samples);
+}
+
+/**************************************************************/
+/* video output */
+
+static AVFrame *picture, *tmp_picture;
+static int frame_count;
+
+/* Add a video output stream. */
+static AVStream *add_video_stream(AVFormatContext *oc, enum AVCodecID codec_id)
+{
+    AVCodecContext *c;
+    AVStream *st;
+    AVCodec *codec;
+
+    /* find the video encoder */
+    codec = avcodec_find_encoder(codec_id);
+    if (!codec) {
+        fprintf(stderr, "codec not found\n");
+        exit(1);
+    }
+
+    st = avformat_new_stream(oc, codec);
+    if (!st) {
+        fprintf(stderr, "Could not alloc stream\n");
+        exit(1);
+    }
+
+    c = st->codec;
+
+    /* Put sample parameters. */
+    c->bit_rate = 400000;
+    /* Resolution must be a multiple of two. */
+    c->width    = 352;
+    c->height   = 288;
+    /* timebase: This is the fundamental unit of time (in seconds) in terms
+     * of which frame timestamps are represented. For fixed-fps content,
+     * timebase should be 1/framerate and timestamp increments should be
+     * identical to 1. */
+    c->time_base.den = STREAM_FRAME_RATE;
+    c->time_base.num = 1;
+    c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
+    c->pix_fmt       = STREAM_PIX_FMT;
+    if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
+        /* just for testing, we also add B frames */
+        c->max_b_frames = 2;
+    }
+    if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
+        /* Needed to avoid using macroblocks in which some coeffs overflow.
+         * This does not happen with normal video, it just happens here as
+         * the motion of the chroma plane does not match the luma plane. */
+        c->mb_decision = 2;
+    }
+    /* Some formats want stream headers to be separate. */
+    if (oc->oformat->flags & AVFMT_GLOBALHEADER)
+        c->flags |= CODEC_FLAG_GLOBAL_HEADER;
+
+    return st;
+}
+
+static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
+{
+    AVFrame *picture;
+    uint8_t *picture_buf;
+    int size;
+
+    picture = av_frame_alloc();
+    if (!picture)
+        return NULL;
+    size        = avpicture_get_size(pix_fmt, width, height);
+    picture_buf = av_malloc(size);
+    if (!picture_buf) {
+        av_free(picture);
+        return NULL;
+    }
+    avpicture_fill((AVPicture *)picture, picture_buf,
+                   pix_fmt, width, height);
+    return picture;
+}
+
+static void open_video(AVFormatContext *oc, AVStream *st)
+{
+    AVCodecContext *c;
+
+    c = st->codec;
+
+    /* open the codec */
+    if (avcodec_open2(c, NULL, NULL) < 0) {
+        fprintf(stderr, "could not open codec\n");
+        exit(1);
+    }
+
+    /* Allocate the encoded raw picture. */
+    picture = alloc_picture(c->pix_fmt, c->width, c->height);
+    if (!picture) {
+        fprintf(stderr, "Could not allocate picture\n");
+        exit(1);
+    }
+
+    /* If the output format is not YUV420P, then a temporary YUV420P
+     * picture is needed too. It is then converted to the required
+     * output format. */
+    tmp_picture = NULL;
+    if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
+        tmp_picture = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
+        if (!tmp_picture) {
+            fprintf(stderr, "Could not allocate temporary picture\n");
+            exit(1);
+        }
+    }
+}
+
+/* Prepare a dummy image. */
+static void fill_yuv_image(AVFrame *pict, int frame_index,
+                           int width, int height)
+{
+    int x, y, i;
+
+    i = frame_index;
+
+    /* Y */
+    for (y = 0; y < height; y++)
+        for (x = 0; x < width; x++)
+            pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
+
+    /* Cb and Cr */
+    for (y = 0; y < height / 2; y++) {
+        for (x = 0; x < width / 2; x++) {
+            pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
+            pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
+        }
+    }
+}
+
+static void write_video_frame(AVFormatContext *oc, AVStream *st)
+{
+    int ret;
+    AVCodecContext *c;
+    static struct SwsContext *img_convert_ctx;
+
+    c = st->codec;
+
+    if (frame_count >= STREAM_NB_FRAMES) {
+        /* No more frames to compress. The codec has a latency of a few
+         * frames if using B-frames, so we get the last frames by
+         * passing the same picture again. */
+    } else {
+        if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
+            /* as we only generate a YUV420P picture, we must convert it
+             * to the codec pixel format if needed */
+            if (img_convert_ctx == NULL) {
+                img_convert_ctx = sws_getContext(c->width, c->height,
+                                                 AV_PIX_FMT_YUV420P,
+                                                 c->width, c->height,
+                                                 c->pix_fmt,
+                                                 sws_flags, NULL, NULL, NULL);
+                if (img_convert_ctx == NULL) {
+                    fprintf(stderr,
+                            "Cannot initialize the conversion context\n");
+                    exit(1);
+                }
+            }
+            fill_yuv_image(tmp_picture, frame_count, c->width, c->height);
+            sws_scale(img_convert_ctx, tmp_picture->data, tmp_picture->linesize,
+                      0, c->height, picture->data, picture->linesize);
+        } else {
+            fill_yuv_image(picture, frame_count, c->width, c->height);
+        }
+    }
+
+    if (oc->oformat->flags & AVFMT_RAWPICTURE) {
+        /* Raw video case - the API will change slightly in the near
+         * future for that. */
+        AVPacket pkt;
+        av_init_packet(&pkt);
+
+        pkt.flags        |= AV_PKT_FLAG_KEY;
+        pkt.stream_index  = st->index;
+        pkt.data          = (uint8_t *)picture;
+        pkt.size          = sizeof(AVPicture);
+
+        ret = av_interleaved_write_frame(oc, &pkt);
+    } else {
+        AVPacket pkt = { 0 };
+        int got_packet;
+        av_init_packet(&pkt);
+
+        /* encode the image */
+        ret = avcodec_encode_video2(c, &pkt, picture, &got_packet);
+        /* If size is zero, it means the image was buffered. */
+        if (!ret && got_packet && pkt.size) {
+            if (pkt.pts != AV_NOPTS_VALUE) {
+                pkt.pts = av_rescale_q(pkt.pts,
+                                       c->time_base, st->time_base);
+            }
+            if (pkt.dts != AV_NOPTS_VALUE) {
+                pkt.dts = av_rescale_q(pkt.dts,
+                                       c->time_base, st->time_base);
+            }
+            pkt.stream_index = st->index;
+
+            /* Write the compressed frame to the media file. */
+            ret = av_interleaved_write_frame(oc, &pkt);
+        } else {
+            ret = 0;
+        }
+    }
+    if (ret != 0) {
+        fprintf(stderr, "Error while writing video frame\n");
+        exit(1);
+    }
+    frame_count++;
+}
+
+static void close_video(AVFormatContext *oc, AVStream *st)
+{
+    avcodec_close(st->codec);
+    av_free(picture->data[0]);
+    av_free(picture);
+    if (tmp_picture) {
+        av_free(tmp_picture->data[0]);
+        av_free(tmp_picture);
+    }
+}
+
+/**************************************************************/
+/* media file output */
+
+int main(int argc, char **argv)
+{
+    const char *filename;
+    AVOutputFormat *fmt;
+    AVFormatContext *oc;
+    AVStream *audio_st, *video_st;
+    double audio_pts, video_pts;
+    int i;
+
+    /* Initialize libavcodec, and register all codecs and formats. */
+    av_register_all();
+
+    if (argc != 2) {
+        printf("usage: %s output_file\n"
+               "API example program to output a media file with libavformat.\n"
+               "The output format is automatically guessed according to the file extension.\n"
+               "Raw images can also be output by using '%%d' in the filename\n"
+               "\n", argv[0]);
+        return 1;
+    }
+
+    filename = argv[1];
+
+    /* Autodetect the output format from the name. default is MPEG. */
+    fmt = av_guess_format(NULL, filename, NULL);
+    if (!fmt) {
+        printf("Could not deduce output format from file extension: using MPEG.\n");
+        fmt = av_guess_format("mpeg", NULL, NULL);
+    }
+    if (!fmt) {
+        fprintf(stderr, "Could not find suitable output format\n");
+        return 1;
+    }
+
+    /* Allocate the output media context. */
+    oc = avformat_alloc_context();
+    if (!oc) {
+        fprintf(stderr, "Memory error\n");
+        return 1;
+    }
+    oc->oformat = fmt;
+    snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
+
+    /* Add the audio and video streams using the default format codecs
+     * and initialize the codecs. */
+    video_st = NULL;
+    audio_st = NULL;
+    if (fmt->video_codec != AV_CODEC_ID_NONE) {
+        video_st = add_video_stream(oc, fmt->video_codec);
+    }
+    if (fmt->audio_codec != AV_CODEC_ID_NONE) {
+        audio_st = add_audio_stream(oc, fmt->audio_codec);
+    }
+
+    /* Now that all the parameters are set, we can open the audio and
+     * video codecs and allocate the necessary encode buffers. */
+    if (video_st)
+        open_video(oc, video_st);
+    if (audio_st)
+        open_audio(oc, audio_st);
+
+    av_dump_format(oc, 0, filename, 1);
+
+    /* open the output file, if needed */
+    if (!(fmt->flags & AVFMT_NOFILE)) {
+        if (avio_open(&oc->pb, filename, AVIO_FLAG_WRITE) < 0) {
+            fprintf(stderr, "Could not open '%s'\n", filename);
+            return 1;
+        }
+    }
+
+    /* Write the stream header, if any. */
+    avformat_write_header(oc, NULL);
+
+    for (;;) {
+        /* Compute current audio and video time. */
+        if (audio_st)
+            audio_pts = (double)audio_st->pts.val * audio_st->time_base.num / audio_st->time_base.den;
+        else
+            audio_pts = 0.0;
+
+        if (video_st)
+            video_pts = (double)video_st->pts.val * video_st->time_base.num /
+                        video_st->time_base.den;
+        else
+            video_pts = 0.0;
+
+        if ((!audio_st || audio_pts >= STREAM_DURATION) &&
+            (!video_st || video_pts >= STREAM_DURATION))
+            break;
+
+        /* write interleaved audio and video frames */
+        if (!video_st || (video_st && audio_st && audio_pts < video_pts)) {
+            write_audio_frame(oc, audio_st);
+        } else {
+            write_video_frame(oc, video_st);
+        }
+    }
+
+    /* Write the trailer, if any. The trailer must be written before you
+     * close the CodecContexts open when you wrote the header; otherwise
+     * av_write_trailer() may try to use memory that was freed on
+     * av_codec_close(). */
+    av_write_trailer(oc);
+
+    /* Close each codec. */
+    if (video_st)
+        close_video(oc, video_st);
+    if (audio_st)
+        close_audio(oc, audio_st);
+
+    /* Free the streams. */
+    for (i = 0; i < oc->nb_streams; i++) {
+        av_freep(&oc->streams[i]->codec);
+        av_freep(&oc->streams[i]);
+    }
+
+    if (!(fmt->flags & AVFMT_NOFILE))
+        /* Close the output file. */
+        avio_close(oc->pb);
+
+    /* free the stream */
+    av_free(oc);
+
+    return 0;
+}