[FFmpeg-devel] encoding/decoding h.264

Peter Wilkes pwilkes
Thu Dec 13 18:23:16 CET 2007


i am trying to build a project using ffmpeg that will encode/decode h. 
264 data.

we have an RGB24 image and we would like a decoded RGB24 image on the  

i am trying to setup ffmpeg to do this for me and i am having  
difficulty getting the parameters correct.

i know i need to do a RGB24->YUV420 conversion which i do using  
sws_scale before encoding
i know i need to do a YUV420->RGB24 conversion which i do using  
sws_scale after decoding.

i know that the sws_scale before the encode and after the decode work  
because if i comment out the encode/decode the original image shows  
(minus conversion differences)

for encoding i have set up the following parameters

encoder = avcodec_alloc_context();
encoder->bit_rate = 16 * 1000;
encoder->rc_max_rate = 16 * 1000;
encoder->width = 160;
encoder->height = 120;

encoder->time_base.num = 1;
encoder->time_base.den = 30;
encoder->gop_size = 10;
encoder->max_b_frames = 1;
encoder->pix_fmt = PIX_FMT_YUV420P;

my decoder settings are

decoder = avcodec_alloc_context();
decoder->width = 160;
decoder->height = 120;
decoder->pix_fmt = PIX_FMT_YUV420P;

i do get a picture out but it looks nothing like my original picture.

any assistance anyone can provide would very much be appreciated.

Peter Wilkes

More information about the ffmpeg-devel mailing list