When we need to force AudioDecode or VideoDecode?

Hi, I was trying to use FFMpegInterop in windows phone 8.1, everything works fine, but in some of videos needs forceAudioDecode to be true (because when I put false in parameter, audio is spoiled)

In videos that didn't need to force AudioDecode to be true, when I true the audio decoding, audio + video playing its very fast, looks like player is in fast forward mode!

With pot player for Windows I found this:
for video that didn't need to force Audio decoding to be true:

General
Unique ID : 60079824637526059836669318900286688400 (0x2D32F40D95D34A41DF13E6E9647B0C90)
Complete name : C:\Users\admin\Downloads\Video\Dark.Matter.S01E06.480p.mkv
Format : Matroska
Format version : Version 4 / Version 2
File size : 150 MiB
Duration : 42mn 57s
Overall bit rate : 488 Kbps
Movie name : Dark Matter S01E06 - RMTeam
Writing application : Lavf56.40.101
Writing library : Lavf56.40.101
DESCRIPTION : Encoded By RMTeam

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.1
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Codec ID : V_MPEG4/ISO/AVC
Width : 854 pixels
Height : 480 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Writing library : x264 core 146 r109 121396c
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-2 / threads=8 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=8 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=24.5 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=10000 / vbv_bufsize=10000 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00
Language : English
Default : Yes
Forced : No

Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : A_AAC
Duration : 42mn 57s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz
Compression mode : Lossy
Writing library : Lavc56.49.101 aac
Default : Yes
Forced : No

and a video that need force Audio decoding to true:
General
Unique ID : 184677726890362367291245475020848181446 (0x8AEFA2ECF136B19B988E4E2442EF30C6)
Complete name : C:\Users\admin\Downloads\Video\Inside.Out.2015.720p.HDRip.mkv
Format : Matroska
Format version : Version 4 / Version 2
File size : 702 MiB
Duration : 1h 34mn
Overall bit rate : 1 038 Kbps
Movie name : Inside Out
Encoded date : UTC 2015-09-28 20:01:12
Writing application : mkvmerge v8.3.0 ('Over the Horizon') 64bit
Writing library : libebml v1.3.1 + libmatroska v1.4.2
DURATION : 00:58:26.057000000
NUMBER_OF_FRAMES : 3
NUMBER_OF_BYTES : 276
_STATISTICS_WRITING_APP : mkvmerge v8.3.0 ('Over the Horizon') 64bit
_STATISTICS_WRITING_DATE_UTC : 2015-09-28 20:01:12
_STATISTICS_TAGS : BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 5 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 34mn
Nominal bit rate : 972 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 30.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.035
Writing library : x264 core 146 r2538 121396c
Encoding settings : cabac=1 / ref=5 / deblock=1👎-1 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=300 / keyint_min=30 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=2pass / mbtree=1 / bitrate=972 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=62500 / vbv_bufsize=78125 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00
Default : Yes
Forced : No

Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : HE-AAC / LC
Codec ID : A_AAC
Duration : 1h 34mn
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz / 24.0 KHz
Compression mode : Lossy
Delay relative to video : 31ms
Default : Yes
Forced : No

so When we need to force AudioDecode ?
How can I programmatically know when I need to force Audio decoding to true?

thanks

No source file or test is named. Start by reproducing the two MKV playback cases in Windows Phone 8.1 and inspect how FFMpegInterop handles the forceAudioDecode parameter; the issue is complete only when the triggering conditions and expected handling are established.