[HELP] MP4 PCM error

[ssdde]

a video file is MKV, x264+PCM

i want to encode it to a MP4, X264+PCM, but Hybrid displayed this:


is that mean MP4 file can't with PCM audio? i have to using AAC or AC3 audio format to encode?

is there anyway to encode MP4, x264+PCM?  because i want to keep the best quality

and the PCM info is

Format                        : PCM
Format settings                : Little / Signed
Codec ID                      : A_PCM/INT/LIT
Duration                      : 44 min 47 s
Bit rate mode                  : Constant
Bit rate                      : 1 536 kb/s
Channel(s)                    : 2 channels
Sampling rate                  : 48.0 kHz
Frame rate                    : 2.000 FPS (24000 SPF)
Bit depth                      : 16 bits
Stream size                    : 492 MiB (3%)


if i only have to encode it with X264+AAC, what's the best bitrate of AAC to set? can it reach 3072 or 1510?