user35620: I just want to crop 2 pixels (Top) to get identical black bars (now is 138 TOP and 140 BOTTOM) but without re-encoding. I think it is possible with FFmpeg but I'm not sure. I want to do this with one H264 video (m2ts from blu-ray).

user1871: You can use the h264_metadata bitstream filter.
ffmpeg -i in -c copy -bsf:v h264_metadata=crop_top=140 out


35620: <p>I just want to crop 2 pixels (Top) to get identical black bars (now is 138 TOP and 140 BOTTOM) but without re-encoding. I think it is possible with FFmpeg but I'm not sure. I want to do this with one H264 video (m2ts from blu-ray).</p>
 1871: <p>You can use the <a href="http://www.ffmpeg.org/ffmpeg-bitstream-filters.html#h264_005fmetadata" rel="nofollow noreferrer">h264_metadata</a> bitstream filter.</p>
<pre><code>ffmpeg -i in -c copy -bsf:v h264_metadata=crop_top=140 out
</code></pre>
