[Libav-user] Need help on encoding

[Thomas]

Hi,
I need a little help on video. What I want to do is to modify a motion vector to embed some datas (I do steganography in research) and to write a new video with out loss of datas.

Currently I can write a video (just with I-frames and P-frames no
B-frames) but it seems that at a moment a filter came and erase my datas. So is there any options to deactivate filters ?
I find a me_method to do that but it seems it doesn't work. I use it like that :
AVDictionary *opts = NULL;
av_dict_set(&opts, "crf", "0", 0);
av_dict_set(&opts, "preset", "placebo", 0); av_dict_set(&opts,"me_method","zero",0);
av_dict_set(&opts,"flags","nomc",0);
if (avcodec_open2(m_stream->codec, m_codec, &opts) < 0) {   throw -108;}
Thank you for your help,
Best regards,
Delmas P.



I guess you must add your Metadata after encoding to the encoded frame. 
But I do not have a solution how to  do it exactly, it may also depend on the container format you use.

A long time a go I'd had a ffmpeg project and I must also put some extra data to every frame and if I remember correctly, I put it in an extra file with some kind of frame identifier, because I did'nt found a way , but this is 10 years ago.

Thomas