[FFmpeg-user] Converting audio to mono to mp4 output

[Alexandr Němec]

Hi all, doing 
 
ffmpeg -i input.avi -c:v h264 -g 30 -bf 0 -c:a aac -ac 1 test.mp4
 
should produce a single audio channel in the output file. Dumping the resulting mp4 file (see the important part below) I can see that channel_count is still 2. What am I misundestanding here?
 
Thank you.
 
Alex
 
 
.....
[mp4a] size=8+102
              data_reference_index = 1
              channel_count = 2
              sample_size = 16
              sample_rate = 44100
              [esds] size=12+42
                [ESDescriptor] size=5+37
                  es_id = 2
                  stream_priority = 0
                  [DecoderConfig] size=5+23
                    stream_type = 5
                    object_type = 64
                    up_stream = 0
                    buffer_size = 0
                    max_bitrate = 69830
                    avg_bitrate = 69830
                    DecoderSpecificInfo = 12 08 56 e5 00