FFMpeg(Android) av_read_frame or avcodec_decode_video2 returning same colour

Question

I've been experimenting FFMpeg for the past 2 weeks and I'm having a bit of trouble... First I've been working with a Galaxy S3, which worked super fine, gave me the best pictures ever but I recently switched to a Galaxy NEXUS which gave me a bunch of problems...

What I'm doing : I just extract frame from a video

How I'm doing :

while(av_read_frame(gFormatCtx, &packet)>=0)
        {
            // Is this a packet from the video stream?
            if(packet.stream_index==videoStream)
            {
                // Decode video frame
                avcodec_decode_video2(gVideoCodecCtx, pFrame, &frameFinished, &packet);
                // Did we get a video frame?
                if(frameFinished)
                {//and so on... But our problem is already here...

Ok, now pFrame is holding a YUV representation of my frame... So, in order to check what I'm getting from the avcodec_decode_video2(...) function I'm just writing pFrame to a file so I can see it with any YUV reader on the web.

char yuvFileName[100];
sprintf(yuvFileName,"/storage/sdcard0/yuv%d.yuv",index);
FILE* fp = fopen(yuvFileName, "wb");
int y;
// Write pixel data
for(y=0; y<gVideoCodecCtx->height; y++)
{
    fwrite(pFrame->data[0]+y*pFrame->linesize[0], 1, gVideoCodecCtx->width, fp);    
}
for(y=0; y<gVideoCodecCtx->height/2; y++)
{
    fwrite(pFrame->data[1]+y*pFrame->linesize[1], 1, gVideoCodecCtx->width/2, fp);
}
for(y=0; y<gVideoCodecCtx->height/2; y++)
{
    fwrite(pFrame->data[2]+y*pFrame->linesize[2], 1, gVideoCodecCtx->width/2, fp);
}
fclose(fp);

Ok so Here I now have my result on a file store @ /storage/sdcard0/blabla.YUV on my Galaxy Nexus root memory.

But If I open the file with (for example XnView, which is meant to display YUV type properly) I only see Dark green on the picture.

What bothers me is that everything worked properly on Galaxy S3 but something failed on GNexus...

So here's my question : Why doesn't it work on Galaxy Nexus ?

Compatibility problem between Gnexus and armeabiv7 ?

I don't know !

Regards, Cehm

score 2 · Accepted Answer · answered Dec 05 '12 at 08:25

2

May be your frames was not decoded well, because decodec did not get keyframe yet. That's happened to me when i was processing live streams. So wait for first keyframe before u will save produced frame. And use pFrame->width rather than gVideoCodecCtx->width

answered Dec 05 '12 at 08:25

Santa77

36
2

Well, in fact it appears that on the Galaxy Nexus the first few frames are totally black... After passing the first 12 to 25 frames everything goes fine again. – Cehm Dec 05 '12 at 13:13

FFMpeg(Android) av_read_frame or avcodec_decode_video2 returning same colour

1 Answers1