Not able to decode mp4 file using latest ffmpeg library : av_decode_video2 - c

Question

I am writing a wrapper code around latest ffmpeg library. I am supplying MP4 files from local system. My problem is that I am unable to get any decoded frames when I use av_decode_video2(). The return value comes out to be negative. I have used av_read_frame() which returns 0. I googled about the problem I am facing but no where could I find the correct explanation. Please give me insight here. Pasting the pseudo code here.
av_init_packet(avpkt);
picture=av_frame_alloc();
pFrameRGB=av_frame_alloc();
codec = avcodec_find_decoder(CODEC_ID_H264);
c= avcodec_alloc_context3(codec)
avcodec_open2(decoderLibraryData->c, decoderLibraryData->codec, NULL)
FormatContext = avformat_alloc_context();
char *pUrl ="./1.MP4";
iRet = avformat_open_input(atContext, pUrl, pFmt, NULL);
if(FormatContext == NULL)
{
printf("could not assign any memory !!!!!!!!! \n");
}
avformat_find_stream_info(FormatContext, NULL);
while(av_read_frame(FormatContext,avpkt) >= 0)
{
len = avcodec_decode_video2(c, picture, &got_picture,avpkt);
printf("CODEC MANAGER len %d Frame decompressed %d \n",len,got_picture);
if (len <= 0)
{
return ERROR;
}
}
}
if(lastHeight != 0 && lastWidth != 0)
{
if(lastWidth != c->width || lastHeight != c->height )
{
av_free(buffer);
buffer = NULL;
lastWidth = c->width;
lastHeight = c->height;
}
}
else
{
lastWidth = c->width;
lastHeight = c->height;
}
decodeFlag = 1;
if(!buffer)
{
int numBytes;
v_mutex_lock(globalCodecLock);
switch(inPixFormat)
{
case RGB:
// Determine required buffer size and allocate buffer
numBytes=avpicture_get_size(PIX_FMT_RGB24, c->width, c->height);
buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
avpicture_fill((AVPicture *)pFrameRGB,buffer,PIX_FMT_RGB24,c->width, c->height);
if(cntxt)
sws_freeContext(cntxt);
cntxt = sws_getContext(c->width, c->height, c->pix_fmt,
c->width, c->height, PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);
break;
}
v_mutex_unlock(globalCodecLock);
if(cntxt == NULL)
{
printf("sws_getContext error\n");
return ERROR;
}
}
{
sws_scale(cntxt, picture->data, picture->linesize, 0, c->height, pFrameRGB->data, pFrameRGB->linesize);
if(rgbBuff)
{
if(c->width <= *width && c->height <= *height)
{
saveFrame(pFrameRGB, c->width, c->height, rgbBuff,inPixFormat);
*width = c->width;
*height = c->height;
rs = SUCCESS;
break;
}
else
{
rs = VA_LOWBUFFERSIZE;
}
}
else
{
rs = VA_LOWBUFFERSIZE;
}
}
if(width)
{
*width = c->width;
}
if(height)
{
*height = c->height;
}
if(rs == VA_LOWBUFFERSIZE)
{
break;
}
I am getting the return value of av_read_frame as 0 but av_decode_video2 returns value in negative. I am not able to get any clue here.

Answer 1

Make sure you have called
av_register_all();
or
avcodec_register_all();
at the beginning of your app.
Also it seems the problem is from calling avformat_find_stream_info. Test with the following code:
AVPacket avpkt;
av_init_packet(&avpkt);
AVFrame* picture = av_frame_alloc();
AVFrame* pFrameRGB = av_frame_alloc();
AVFormatContext* c2 = avformat_alloc_context();
char *pUrl = "C:/Sample Videos/20-06-34.MP4";
int video_stream_index = 0;
AVInputFormat* pFmt;
int iRet = avformat_open_input(&c2, pUrl, pFmt, NULL);
AVStream* stream = c2->streams[video_stream_index];
AVCodec* codec = avcodec_find_decoder(stream->codec->codec_id);
avcodec_open2(stream->codec, codec, NULL);
if (c2 == NULL)
{
printf("could not assign any memory !!!!!!!!! \n");
}
while (av_read_frame(c2, &avpkt) >= 0)
{
int got_picture;
int len = avcodec_decode_video2(stream->codec, picture, &got_picture, &avpkt);
printf("CODEC MANAGER len %d Frame decompressed %d \n", len, got_picture);
if (len <= 0)
{
return ERROR;
}
}