From de6d9b6404bfd1c589799142da5a95428f146edd Mon Sep 17 00:00:00 2001
From: Fabrice Bellard <fabrice@bellard.org>
Date: Sun, 22 Jul 2001 14:18:56 +0000
Subject: Initial revision

Originally committed as revision 5 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/apiexample.c | 407 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 407 insertions(+)
 create mode 100644 libavcodec/apiexample.c

(limited to 'libavcodec/apiexample.c')

diff --git a/libavcodec/apiexample.c b/libavcodec/apiexample.c
new file mode 100644
index 0000000000..e7ae6e80be
--- /dev/null
+++ b/libavcodec/apiexample.c
@@ -0,0 +1,407 @@
+/* avcodec API use example.
+ *
+ * Note that this library only handles codecs (mpeg, mpeg4, etc...),
+ * not file formats (avi, vob, etc...). See library 'libav' for the
+ * format handling 
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+#include "avcodec.h"
+
+#define INBUF_SIZE 4096
+
+/*
+ * Audio encoding example 
+ */
+void audio_encode_example(const char *filename)
+{
+    AVCodec *codec;
+    AVCodecContext codec_context, *c = &codec_context;
+    int frame_size, i, j, out_size, outbuf_size;
+    FILE *f;
+    short *samples;
+    float t, tincr;
+    UINT8 *outbuf;
+
+    printf("Audio encoding\n");
+
+    /* find the MP2 encoder */
+    codec = avcodec_find_encoder(CODEC_ID_MP2);
+    if (!codec) {
+        fprintf(stderr, "codec not found\n");
+        exit(1);
+    }
+
+    /* put default values */
+    memset(c, 0, sizeof(*c));
+
+    /* put sample parameters */
+    c->bit_rate = 64000;
+    c->sample_rate = 44100;
+    c->channels = 2;
+
+    /* open it */
+    if (avcodec_open(c, codec) < 0) {
+        fprintf(stderr, "could not open codec\n");
+        exit(1);
+    }
+    
+    /* the codec gives us the frame size, in samples */
+    frame_size = c->frame_size;
+    samples = malloc(frame_size * 2 * c->channels);
+    outbuf_size = 10000;
+    outbuf = malloc(outbuf_size);
+
+    f = fopen(filename, "w");
+    if (!f) {
+        fprintf(stderr, "could not open %s\n", filename);
+        exit(1);
+    }
+        
+    /* encode a single tone sound */
+    t = 0;
+    tincr = 2 * M_PI * 440.0 / c->sample_rate;
+    for(i=0;i<200;i++) {
+        for(j=0;j<frame_size;j++) {
+            samples[2*j] = (int)(sin(t) * 10000);
+            samples[2*j+1] = samples[2*j];
+            t += tincr;
+        }
+        /* encode the samples */
+        out_size = avcodec_encode_audio(c, outbuf, outbuf_size, samples);
+        fwrite(outbuf, 1, out_size, f);
+    }
+    fclose(f);
+    free(outbuf);
+    free(samples);
+
+    avcodec_close(c);
+}
+
+/*
+ * Audio decoding. 
+ */
+void audio_decode_example(const char *outfilename, const char *filename)
+{
+    AVCodec *codec;
+    AVCodecContext codec_context, *c = &codec_context;
+    int out_size, size, len;
+    FILE *f, *outfile;
+    UINT8 *outbuf;
+    UINT8 inbuf[INBUF_SIZE], *inbuf_ptr;
+
+    printf("Audio decoding\n");
+
+    /* find the mpeg audio decoder */
+    codec = avcodec_find_decoder(CODEC_ID_MP2);
+    if (!codec) {
+        fprintf(stderr, "codec not found\n");
+        exit(1);
+    }
+
+    /* put default values */
+    memset(c, 0, sizeof(*c));
+
+    /* open it */
+    if (avcodec_open(c, codec) < 0) {
+        fprintf(stderr, "could not open codec\n");
+        exit(1);
+    }
+    
+    outbuf = malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE);
+
+    f = fopen(filename, "r");
+    if (!f) {
+        fprintf(stderr, "could not open %s\n", filename);
+        exit(1);
+    }
+    outfile = fopen(outfilename, "w");
+    if (!outfile) {
+        fprintf(stderr, "could not open %s\n", outfilename);
+        exit(1);
+    }
+        
+    /* decode until eof */
+    inbuf_ptr = inbuf;
+    for(;;) {
+        size = fread(inbuf, 1, INBUF_SIZE, f);
+        if (size == 0)
+            break;
+
+        inbuf_ptr = inbuf;
+        while (size > 0) {
+            len = avcodec_decode_audio(c, (short *)outbuf, &out_size, 
+                                       inbuf_ptr, size);
+            if (len < 0) {
+                fprintf(stderr, "Error while decoding\n");
+                exit(1);
+            }
+            if (out_size > 0) {
+                /* if a frame has been decoded, output it */
+                fwrite(outbuf, 1, out_size, outfile);
+            }
+            size -= len;
+            inbuf_ptr += len;
+        }
+    }
+
+    fclose(outfile);
+    fclose(f);
+    free(outbuf);
+
+    avcodec_close(c);
+}
+
+/*
+ * Video encoding example 
+ */
+void video_encode_example(const char *filename)
+{
+    AVCodec *codec;
+    AVCodecContext codec_context, *c = &codec_context;
+    int i, out_size, size, x, y, outbuf_size;
+    FILE *f;
+    AVPicture picture;
+    UINT8 *outbuf, *picture_buf;
+
+    printf("Video encoding\n");
+
+    /* find the mpeg1 video encoder */
+    codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
+    if (!codec) {
+        fprintf(stderr, "codec not found\n");
+        exit(1);
+    }
+
+    /* put default values */
+    memset(c, 0, sizeof(*c));
+
+    /* put sample parameters */
+    c->bit_rate = 400000;
+    /* resolution must be a multiple of two */
+    c->width = 352;  
+    c->height = 288;
+    /* frames per second */
+    c->frame_rate = 25 * FRAME_RATE_BASE;  
+    c->gop_size = 10; /* emit one intra frame every ten frames */
+
+    /* open it */
+    if (avcodec_open(c, codec) < 0) {
+        fprintf(stderr, "could not open codec\n");
+        exit(1);
+    }
+    
+    /* the codec gives us the frame size, in samples */
+
+    f = fopen(filename, "w");
+    if (!f) {
+        fprintf(stderr, "could not open %s\n", filename);
+        exit(1);
+    }
+    
+    /* alloc image and output buffer */
+    outbuf_size = 100000;
+    outbuf = malloc(outbuf_size);
+    size = c->width * c->height;
+    picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */
+    
+    picture.data[0] = picture_buf;
+    picture.data[1] = picture.data[0] + size;
+    picture.data[2] = picture.data[1] + size / 4;
+    picture.linesize[0] = c->width;
+    picture.linesize[1] = c->width / 2;
+    picture.linesize[2] = c->width / 2;
+
+    /* encode 1 second of video */
+    for(i=0;i<25;i++) {
+        printf("encoding frame %3d\r", i);
+        fflush(stdout);
+        /* prepare a dummy image */
+        /* Y */
+        for(y=0;y<c->height;y++) {
+            for(x=0;x<c->width;x++) {
+                picture.data[0][y * picture.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++) {
+                picture.data[1][y * picture.linesize[1] + x] = 128 + y + i * 2;
+                picture.data[2][y * picture.linesize[2] + x] = 64 + x + i * 5;
+            }
+        }
+
+        /* encode the image */
+        out_size = avcodec_encode_video(c, outbuf, outbuf_size, &picture);
+        fwrite(outbuf, 1, out_size, f);
+    }
+
+    /* add sequence end code to have a real mpeg file */
+    outbuf[0] = 0x00;
+    outbuf[1] = 0x00;
+    outbuf[2] = 0x01;
+    outbuf[3] = 0xb7;
+    fwrite(outbuf, 1, 4, f);
+    fclose(f);
+    free(picture_buf);
+    free(outbuf);
+
+    avcodec_close(c);
+    printf("\n");
+}
+
+/*
+ * Video decoding example 
+ */
+
+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);
+}
+
+void video_decode_example(const char *outfilename, const char *filename)
+{
+    AVCodec *codec;
+    AVCodecContext codec_context, *c = &codec_context;
+    int frame, size, got_picture, len;
+    FILE *f;
+    AVPicture picture;
+    UINT8 inbuf[INBUF_SIZE], *inbuf_ptr;
+    char buf[1024];
+
+    printf("Video decoding\n");
+
+    /* find the mpeg1 video decoder */
+    codec = avcodec_find_decoder(CODEC_ID_MPEG1VIDEO);
+    if (!codec) {
+        fprintf(stderr, "codec not found\n");
+        exit(1);
+    }
+
+    /* put default values */
+    memset(c, 0, sizeof(*c));
+
+    /* for some codecs, such as msmpeg4 and opendivx, width and height
+       MUST be initialized there because these info are not available
+       in the bitstream */
+
+    /* open it */
+    if (avcodec_open(c, codec) < 0) {
+        fprintf(stderr, "could not open codec\n");
+        exit(1);
+    }
+    
+    /* the codec gives us the frame size, in samples */
+
+    f = fopen(filename, "r");
+    if (!f) {
+        fprintf(stderr, "could not open %s\n", filename);
+        exit(1);
+    }
+    
+    frame = 0;
+    for(;;) {
+        size = fread(inbuf, 1, INBUF_SIZE, f);
+        if (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, opendivx) 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 */
+        inbuf_ptr = inbuf;
+        while (size > 0) {
+            len = avcodec_decode_video(c, &picture, &got_picture, 
+                                       inbuf_ptr, size);
+            if (len < 0) {
+                fprintf(stderr, "Error while decoding frame %d\n", frame);
+                exit(1);
+            }
+            if (got_picture) {
+                printf("saving frame %3d\r", 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++;
+            }
+            size -= len;
+            inbuf_ptr += 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 */
+    len = avcodec_decode_video(c, &picture, &got_picture, 
+                               NULL, 0);
+    if (got_picture) {
+        printf("saving frame %3d\r", 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);
+    printf("\n");
+}
+
+
+int main(int argc, char **argv)
+{
+    const char *filename;
+
+    /* must be called before using avcodec lib */
+    avcodec_init();
+
+    /* register all the codecs (you can also register only the codec
+       you wish to have smaller code */
+    avcodec_register_all();
+    
+    if (argc <= 1) {
+        audio_encode_example("/tmp/test.mp2");
+        audio_decode_example("/tmp/test.sw", "/tmp/test.mp2");
+
+        video_encode_example("/tmp/test.mpg");
+        filename = "/tmp/test.mpg";
+    } else {
+        filename = argv[1];
+    }
+
+    //    audio_decode_example("/tmp/test.sw", filename);
+    video_decode_example("/tmp/test%d.pgm", filename);
+
+    return 0;
+}
-- 
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