How to read game animation file?

Question

C++ / C#

Good day everyone! I need to convert animations from Metro 2033 to normal fbx format. So far, I only roughly understand that in some order the id of a chunk, the size, and then the matrix of the position of the bones and their rotation. Wrote a script, but it doesn't work very well.

My broken code

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;
using Gibbed.IO;

namespace Metro_2033_SDK_Tools
{
    public partial class ConvertAnimation : Form
    {
        protected const UInt32 MC_HeaderChunk   = 0x00000000,
                               MC_InfoChunk     = 0x00000001,
                               MC_DataChunk     = 0x00000009;

        public ConvertAnimation()
        {
            InitializeComponent();
        }

        private void convert_Click(object sender, EventArgs e)
        {
            mtnOpen.Title = "Метро 2033 анимации";
            mtnOpen.Filter = "Анимации \"Метро 2033\"(*.motion)|*.motion|Все файлы(*.*)|*.*";
            mtnOpen.DefaultExt = "*.motion";
            mtnOpen.ShowDialog();

            string path = mtnOpen.FileName;
            convertPath.Text = path;

            using (Stream input = File.OpenRead(path))
            {
                while (input.Position < (input.Length - 7))
                {
                    UInt32 chunkId = input.ReadValueU32();
                    UInt32 chunkSize = input.ReadValueU32();
                    UInt64 ChunkEnd = (ulong)input.Position + chunkSize;

                    UInt32 mMotionsDataSize = 0;
                    switch (chunkId)
                    {
                        case MC_HeaderChunk:
                            UInt32 mVer         = input.ReadValueU32();
                            UInt32 mBonesCRC    = input.ReadValueU32();
                            UInt16 mNumBones    = input.ReadValueU16();
                            UInt16 mNumLocators = input.ReadValueU16();
                            break;

                        case MC_InfoChunk:
                            UInt16 mFlags   = input.ReadValueU16();

                            float mSpeed    = input.ReadValueF32();
                            float mAccrue = input.ReadValueF32();
                            float mFalloff = input.ReadValueF32();

                            UInt32 mNumKeys = input.ReadValueU32();
                            UInt16 mJumpFrame = input.ReadValueU16();
                            UInt16 mLandFrame = input.ReadValueU16();

                            BitArray mAffectedBones = new BitArray(256);
                            mAffectedBones = input.ReadStructure<BitArray>();

                            mMotionsDataSize = input.ReadValueU32();
                            UInt32 mMotionsOffsetsSize = input.ReadValueU32();

                            BitArray mHighQualityBones = new BitArray(256);
                            mAffectedBones = input.ReadStructure<BitArray>();

                            MessageBox.Show(mMotionsDataSize.ToString());
                            break;

                        case MC_DataChunk:
                            bool mAssert = mMotionsDataSize == chunkSize;
                            MessageBox.Show(String.Format("{0} - assert; {1} - size", mAssert.ToString(), chunkSize.ToString()));
                            break;
                    }
                }
            }
        }
    }
}

Here is an archive with some animations of the game: link