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• How to change wave file frequency while retaining sample rate [duplicate]

  28 janvier 2019, par q1w2e3r4t5y6

  This question already has an answer here :

  • FFMPEG change Tone Frequency (Pitch Audio)
    
    2 answers
    

  I am wondering how to change a wave file’s frequency while retaining its sample rate. I have tried :

  ffmpeg -i $1 -filter:a "asetrate=$2" -y $3

  The second argument here changes drastically, by the way. However, this changes the sample rate, making it impossible to concatenate with sox. How can I modify the above code so that it changes the frequency while still having the same sample rate ?

• avformat/movenc : Add more error checking when writing sample entries.

  5 février 2019, par Nikolas Bowe

  avformat/movenc : Add more error checking when writing sample entries.
  Fixes a problem where a sample entry which cannot be written correctly appears to succeed, but produces an invalid file.
  
  For example, this command :
  
  ffmpeg -f lavfi -i sine=frequency=1000:duration=5 -codec:a ac3 -movflags +empty_moov -frag_duration 5000000 /tmp/foo.mp4
  
  produced a file with the ac-3 sample entry, but no AC3SpecificBox (dac3) child, which is invalid according to ETSI TS 102 366.
  Reviewed-by : Baptiste Coudurier <baptiste.coudurier@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/movenc.c

• FFmpeg sample code for creating a video file from still images JNI Android

  21 juin 2012, par anish

  How i modify the following FFMPEG sample code for creating a video file from still images that i am having in my android phone. I am using JNI for invoking ffmpeg.

  JNIEXPORT void JNICALL videoEncodeExample((JNIEnv *pEnv, jobject pObj, jstring filename)
  
  
  
      {
  
       AVCodec *codec;
  
       AVCodecContext *c= NULL;
  
       int i, out_size, size, x, y, outbuf_size;
  
       FILE *f;
  
       AVFrame *picture;
  
       uint8_t *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);
  
       }
  
  
  
       c= avcodec_alloc_context();
  
       picture= avcodec_alloc_frame();
  
  
  
       /* 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 = PIX_FMT_YUV420P;
  
  
  
       /* open it */
  
       if (avcodec_open(c, codec) < 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);
  
       }
  
  
  
       /* 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++) {
  
           fflush(stdout);
  
           /* prepare a dummy image */
  
           /* Y */
  
           for(y=0;yheight;y++) {
  
               for(x=0;xwidth;x++) {
  
                   picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
               }
  
           }
  
  
  
           /* Cb and Cr */
  
           for(y=0;yheight/2;y++) {
  
               for(x=0;xwidth/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);
  
           printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
           fwrite(outbuf, 1, out_size, f);
  
       }
  
  
  
       /* get the delayed frames */
  
       for(; out_size; i++) {
  
           fflush(stdout);
  
  
  
           out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
           printf("write frame %3d (size=%5d)\n", i, out_size);
  
           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);
  
       av_free(c);
  
       av_free(picture);
  
       printf("\n");
  
      }

  Thanks and Regards
  Anish