C# *ポインタがのenumにアドレスのenumが設定できない原因が知りたい。

提示コードの//ここで例外部の行で以下のエラーが発生するのですがこれは何が原因なのでしょうか？同じ状況を再現した実験コードを書きましたが問題なくコンパイルできます。

参考サイト：　https://ufcpp.net/study/csharp/sp_unsafe.html#abst

Error

System.AccessViolationException: 'Attempted to read or write protected memory. This is often an indication that other memory is corrupt.'

実験コード

cs
1using System;
2
3public class Program
4{
5    enum Status
6    {
7        AAA,
8        BBB
9
10    }
11
12    public static void Main()
13    {
14        unsafe
15        {
16            Status status;
17
18            Status* t;
19            t = &status;
20
21
22        }
23    }
24}
25

問題のソースコード

cs
1using FFmpeg.AutoGen;
2
3internal unsafe class Program
4{
5    static int Main(string[] args)
6    {
7        AVFrame* frame;
8        AVPacket* pkt;
9        int i, j, k, ret;
10        short* samples;
11        float t, tincr;
12
13        if (args.Length <= 0)
14        {
15            string executable = Environment.GetCommandLineArgs()[0];
16            //Console.Error.WriteLine($"Usage: {executable} <output file>");
17            //return 0;
18        }
19
20        var filename = "input.flac";
21
22        /* find the MP2 encoder */
23        AVCodec* codec = ffmpeg.avcodec_find_encoder(AVCodecID.AV_CODEC_ID_MPEG4);
24        if (codec == null)
25        {
26            Console.WriteLine("Codec not found");
27            return 1;
28        }
29
30        AVCodecContext* c = ffmpeg.avcodec_alloc_context3(codec);
31        if (c == null)
32        {
33            Console.Error.WriteLine("Could not allocate audio codec context");
34            return 1;
35        }
36
37        /* put sample parameters */
38        c->bit_rate = 64000;
39
40        /* check that the encoder supports s16 pcm input */
41        c->sample_fmt = AVSampleFormat.AV_SAMPLE_FMT_S16;
42///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
43        AVSampleFormat av;//列挙型
44        av = AVSampleFormat.AV_SAMPLE_FMT_S16;
45
46         //codec->sample_fmtsはAVSampleFormat型
47        codec->sample_fmts =  &av;  //ここで例外
48///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
49        *codec->sample_fmts = AVSampleFormat.AV_SAMPLE_FMT_S16;
50        if (!check_sample_fmt(codec, c->sample_fmt))
51        {
52            string sampleFormat = ffmpeg.av_get_sample_fmt_name(c->sample_fmt);
53            Console.Error.WriteLine($"Encoder does not support sample format {sampleFormat}");
54            return 1;
55        }
56
57        /* select other audio parameters supported by the encoder */
58        c->sample_rate = select_sample_rate(codec);
59        c->channel_layout = select_channel_layout(codec);
60        c->channels = ffmpeg.av_get_channel_layout_nb_channels(c->channel_layout);
61
62        /* open it */
63        if (ffmpeg.avcodec_open2(c, codec, null) < 0)
64        {
65            Console.Error.WriteLine($"Could not open codec");
66            return 1;
67        }
68
69        using BinaryWriter output = new BinaryWriter(new FileStream(filename, FileMode.Create));
70
71        /* packet for holding encoded output */
72        pkt = ffmpeg.av_packet_alloc();
73        if (pkt == null)
74        {
75            Console.Error.WriteLine($"could not allocate the packet");
76            return 1;
77        }
78
79        /* frame containing input raw audio */
80        frame = ffmpeg.av_frame_alloc();
81        if (frame == null)
82        {
83            Console.Error.WriteLine($"Could not allocate audio frame");
84            return 1;
85        }
86
87        frame->nb_samples = c->frame_size;
88        frame->format = (int)c->sample_fmt;
89        frame->channel_layout = c->channel_layout;
90
91        /* allocate the data buffers */
92        ret = ffmpeg.av_frame_get_buffer(frame, 0);
93        if (ret < 0)
94        {
95            Console.Error.WriteLine($"Could not allocate audio data buffers");
96            return 1;
97        }
98
99        /* encode a single tone sound */
100        t = 0.0f;
101        tincr = (float)(2 * Math.PI * 440.0 / c->sample_rate);
102        for (i = 0; i < 200; i++)
103        {
104            /* make sure the frame is writable -- makes a copy if the encoder
105             * kept a reference internally */
106            ret = ffmpeg.av_frame_make_writable(frame);
107            if (ret < 0)
108                return 1;
109            samples = (short*)frame->data[0];
110
111            for (j = 0; j < c->frame_size; j++)
112            {
113                samples[2 * j] = (short)(Math.Sin(t) * 10000);
114
115                for (k = 1; k < c->channels; k++)
116                    samples[2 * j + k] = samples[2 * j];
117                t += tincr;
118            }
119            encode(c, frame, pkt, output);
120        }
121
122        /* flush the encoder */
123        encode(c, null, pkt, output);
124
125        ffmpeg.av_frame_free(&frame);
126        ffmpeg.av_packet_free(&pkt);
127        ffmpeg.avcodec_free_context(&c);
128
129        return 0;
130    }
131
132    static void encode(AVCodecContext* ctx, AVFrame* frame, AVPacket* pkt, BinaryWriter output)
133    {
134        int ret;
135
136        /* send the frame for encoding */
137        ret = ffmpeg.avcodec_send_frame(ctx, frame);
138        if (ret < 0)
139        {
140            Console.Error.WriteLine($"Error sending the frame to the encoder");
141            Environment.Exit(1);
142        }
143
144        /* read all the available output packets (in general there may be any
145         * number of them */
146        while (ret >= 0)
147        {
148            ret = ffmpeg.avcodec_receive_packet(ctx, pkt);
149            if (ret == ffmpeg.AVERROR(ffmpeg.EAGAIN) || ret == ffmpeg.AVERROR_EOF)
150                return;
151            else if (ret < 0)
152            {
153                Console.Error.WriteLine($"Error encoding audio frame");
154                Environment.Exit(1);
155            }
156
157            output.Write(new ReadOnlySpan<byte>(pkt->data, pkt->size));
158            ffmpeg.av_packet_unref(pkt);
159        }
160    }
161
162    /* check that a given sample format is supported by the encoder */
163    static bool check_sample_fmt(AVCodec* codec, AVSampleFormat sample_fmt)
164    {
165        AVSampleFormat* p = codec->sample_fmts;
166
167        while (*p != AVSampleFormat.AV_SAMPLE_FMT_NONE)
168        {
169            if (*p == sample_fmt)
170                return true;
171            p++;
172        }
173        return false;
174    }
175
176    /* just pick the highest supported samplerate */
177    static int select_sample_rate(AVCodec* codec)
178    {
179        int best_samplerate = 0;
180
181        if (codec->supported_samplerates == null)
182            return 44100;
183
184        int* p = codec->supported_samplerates;
185        while (*p != 0)
186        {
187            if (best_samplerate != 0 || Math.Abs(44100 - *p) < Math.Abs(44100 - best_samplerate))
188                best_samplerate = *p;
189            p++;
190        }
191        return best_samplerate;
192    }
193
194    /* select layout with the highest channel count */
195    static ulong select_channel_layout(AVCodec* codec)
196    {
197        ulong* p;
198        ulong best_ch_layout = 0;
199        int best_nb_channels = 0;
200
201        if (codec->channel_layouts == null)
202            return ffmpeg.AV_CH_LAYOUT_STEREO;
203
204        p = codec->channel_layouts;
205        while (*p != 0)
206        {
207            int nb_channels = ffmpeg.av_get_channel_layout_nb_channels(*p);
208
209            if (nb_channels > best_nb_channels)
210            {
211                best_ch_layout = *p;
212                best_nb_channels = nb_channels;
213            }
214            p++;
215        }
216
217        return best_ch_layout;
218    }
219}