[FFmpeg-trac] #4404(avcodec:new): Cannot decode PNG or TIF files with libavcodec.

FFmpeg trac at avcodec.org
Mon Mar 30 01:21:09 CEST 2015

#4404: Cannot decode PNG or TIF files with libavcodec.
             Reporter:  sgan         |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avcodec
              Version:  unspecified  |               Resolution:
             Keywords:  PNG          |               Blocked By:
  avcodec_decode_video2              |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |

Comment (by sgan):

 So I am still working on it and I think I finally found the solution.

 As I am not an libavcodec expert, please fill free to comment.

 According to avcodec_open2 documentation,
 ''Prior to using this function the context has to be allocated with

 So new code should be something like that (modifications have been
 commented as //[sgan]:

 int ff_load_image(uint8_t *data[4], int linesize[4],
                   int *w, int *h, enum AVPixelFormat *pix_fmt,
                   const char *filename, void *log_ctx)
     AVInputFormat *iformat = NULL;
     AVFormatContext *format_ctx = NULL;
     AVCodec *codec;
     AVCodecContext *codec_ctx;
     AVFrame *frame;
     int frame_decoded, ret = 0;
     AVPacket pkt;



     iformat = av_find_input_format("image2");
     if ((ret = avformat_open_input(&format_ctx, filename, iformat, NULL))
 < 0) {
         av_log(log_ctx, AV_LOG_ERROR,
                "Failed to open input file '%s'\n", filename);
         return ret;

     if ((ret = avformat_find_stream_info(format_ctx, NULL)) < 0) {
         av_log(log_ctx, AV_LOG_ERROR, "Find stream info failed\n");
         return ret;

     //codec_ctx = format_ctx->streams[0]->codec;            //[sgan]To
     codec = avcodec_find_decoder(codec_ctx->codec_id);   //[sgan]To modify
     if (!codec) {
         av_log(log_ctx, AV_LOG_ERROR, "Failed to find codec\n");
         ret = AVERROR(EINVAL);
         goto end;

     codec_ctx = avcodec_alloc_context3(codec);   //[sgan]To add
       if (!codec_ctx) return -1;                           //[sgan]To add

 //[sgan]To add
 //[sgan]To add
    codec_ctx->pix_fmt=format_ctx->streams[0]->codec->pix_fmt;   //[sgan]To

     if ((ret = avcodec_open2(codec_ctx, codec, NULL)) < 0) {
         av_log(log_ctx, AV_LOG_ERROR, "Failed to open codec\n");
         goto end;

     if (!(frame = av_frame_alloc()) ) {
         av_log(log_ctx, AV_LOG_ERROR, "Failed to alloc frame\n");
         ret = AVERROR(ENOMEM);
         goto end;

     ret = av_read_frame(format_ctx, &pkt);
     if (ret < 0) {
         av_log(log_ctx, AV_LOG_ERROR, "Failed to read frame from file\n");
         goto end;

     ret = avcodec_decode_video2(codec_ctx, frame, &frame_decoded, &pkt);
     if (ret < 0 || !frame_decoded) {
         av_log(log_ctx, AV_LOG_ERROR, "Failed to decode image from
         if (ret >= 0)
             ret = -1;
         goto end;

     *w       = frame->width;
     *h       = frame->height;
     *pix_fmt = frame->format;

     if ((ret = av_image_alloc(data, linesize, *w, *h, *pix_fmt, 16)) < 0)
         goto end;
     ret = 0;

     av_image_copy(data, linesize, (const uint8_t **)frame->data,
 frame->linesize, *pix_fmt, *w, *h);

     //avcodec_close(codec_ctx);               //[sgan]To remove
     avcodec_free_context(&codec_ctx);      //[sgan]To add

     if (ret < 0)
         av_log(log_ctx, AV_LOG_ERROR, "Error loading image file '%s'\n",
     return ret;

 It seems that after:
  codec_ctx = avcodec_alloc_context3(codec);

 , some attibutes have to be set (width,height, ...).

 Now it is working with PNG and TIFF files also.

Ticket URL: <https://trac.ffmpeg.org/ticket/4404#comment:1>
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