avformat/mpegtsenc: More verbose warning messages in case of missing video ES startcodes

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/h264_sei: ff_h264_decode_sei: dont try to parse trailing zeroes

reduces noise for tserrors.ts

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>