How to achive better quality with libav on android surface?

Question

Playing video from RTSP stream on Android surface using solution from this repo https://github.com/alexandruc/android-ffmpeg-player/blob/master/android-ffmpeg-player/jni/ffmpeg-player.c

Video is playng but have a lot of glitches especially when something moving. Have not enought expirience using libav. Will be happy if someone can help or give links on some tutorials or community.

Here is the function to display video on surface.

void* decodeAndRender(void *voidArgs) {
auto *args = (decode_args*)voidArgs;
CamCon* cc = getCamCon(args->name);

ANativeWindow_Buffer    windowBuffer;
AVPacket                packet;
int                     i=0;
int                     frameFinished;
int                     lineCnt;

int counter = 0;
while(av_read_frame(cc->formatCtx, &packet)>=0 && cc->isConnect) {
    counter = 1;
    // Is this a packet from the video stream?
    if(packet.stream_index==cc->videoStreamIdx) {
        // Decode video frame
        avcodec_decode_video2(cc->codecCtx, cc->decodedFrame, &frameFinished, &packet);
        // Did we get a video frame?
        if(frameFinished) {
            // RECORD video
            if(cc->isRecord)
                recordMP4(packet, cc);

            // DISPLAY video
            // Convert the image from its native format to RGBA
            sws_scale (
                    cc->sws_ctx,
                    (uint8_t const * const *)cc->decodedFrame->data,
                    cc->decodedFrame->linesize,
                    0,
                    cc->codecCtx->height,
                    cc->frameRGBA->data,
                    cc->frameRGBA->linesize
            );
            // lock the window buffer
            if (ANativeWindow_lock(cc->window, &windowBuffer, NULL) < 0) {
                LOGE("cannot lock window");
            } else {
                // draw the frame on buffer
                LOGI("copy buffer %d:%d:%d", cc->displayWidth, cc->displayHeight, cc->displayWidth * cc->displayHeight*4);
                LOGI("window buffer: %d:%d:%d", windowBuffer.width,
                     windowBuffer.height, windowBuffer.stride);
                memcpy(windowBuffer.bits, cc->buffer,  cc->displayWidth * cc->displayHeight * 4);
                // unlock the window buffer and post it to display
                ANativeWindow_unlockAndPost(cc->window);
                // count number of frames
                ++i;
            }
        }
    }
    // Free the packet that was allocated by av_read_frame
    av_free_packet(&packet);
}
LOGI("total No. of frames decoded and rendered %d", i);
finish(args->env, args->name);

}