Hi All: My box is CentOS6.5, and FS is 1.6.4 When I use H264 as the video codec. FS report encoding fail as below. [ERR] avcodec.c:1117 Encoding Error -1 and x264 report lookahead thread is already stopped I checked the source code, I found that when switch_h264_encode encode is invoked first time, it results that context->got_encoded_output is set to 1. and after that, if switch_h264_encode is invoked again, it will check context->got_encoded_output , and then pass null frame to avcodec_encode_video2 which will stop the lookahead thread because of the null frame. switch_h264_encode: if (*got_output) { // Could be more delayed frames ret = avcodec_encode_video2(avctx, pkt, NULL, got_output); Is it a bug of mod_av or how can i solve the problem? Thanks a lot