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<h1 style='font-family: Malgun Gothic, Consolas; font-size: 20pt; color: #006699; text-align: center; font-weight: bold'>C# - ffmpeg(FFmpeg.AutoGen)를 이용한 remuxing.c 예제 포팅</h1>

지난 글에 이어, 
 
<pre style='margin: 10px 0px 10px 10px; padding: 10px 0px 10px 10px; background-color: #fbedbb; overflow: auto; font-family: Consolas, Verdana;' >
C# - ffmpeg(FFmpeg.AutoGen)를 이용한 http_multiclient.c 예제 포팅
; <a target='tab' href='https://www.sysnet.pe.kr/2/0/13002'>https://www.sysnet.pe.kr/2/0/13002</a>
</pre>
 
이번에는 <a target='tab' href='https://ffmpeg.org/doxygen/trunk/examples.html'>ffmpeg 예제</a> 중 "<a target='tab' href='https://ffmpeg.org/doxygen/trunk/remuxing_8c-example.html'>remuxing.c</a>" 파일을 FFmpeg.AutoGen으로 포팅하겠습니다. 
 
<pre style='margin: 10px 0px 10px 10px; padding: 10px 0px 10px 10px; background-color: #fbedbb; overflow: auto; font-family: Consolas, Verdana;' >
using FFmpeg.AutoGen;
using FFmpeg.AutoGen.Example;
using System;
using System.IO;

namespace remuxing
{
    internal unsafe class Program
    {
        static unsafe void log_packet(AVFormatContext* fmt_ctx, AVPacket* pkt, string tag)
        {
            AVRational* time_base = &amp;fmt_ctx-&gt;streams[pkt-&gt;stream_index]-&gt;time_base;

Console.WriteLine($"{tag}: pts:{FFmpegHelper.av_ts2str(pkt-&gt;pts)} pts_time:{FFmpegHelper.av_ts2timestr(pkt-&gt;pts, time_base)}"
                + $" dts:{FFmpegHelper.av_ts2str(pkt-&gt;dts)} dts_time:{FFmpegHelper.av_ts2timestr(pkt-&gt;dts, time_base)}"
                + $" duration:{FFmpegHelper.av_ts2str(pkt-&gt;duration)} duration_time:{FFmpegHelper.av_ts2timestr(pkt-&gt;duration, time_base)}"
                + $" stream_index: {pkt-&gt;stream_index}");
        }

static unsafe int Main(string[] args)
        {
            FFmpegBinariesHelper.RegisterFFmpegBinaries();

AVOutputFormat* ofmt = null;
            AVFormatContext* ifmt_ctx = null;
            AVFormatContext* ofmt_ctx = null;
            AVPacket* pkt = null;
            string in_filename, out_filename;
            int ret, i;
            int stream_index = 0;
            int* stream_mapping = null;
            int stream_mapping_size = 0;

string dirPath = Path.GetDirectoryName(typeof(Program).Assembly.Location) ?? "";
            string filename = "sample-10s.mp4";
            in_filename = Path.Combine(dirPath, "..", "..", "..", "Samples", filename);
            out_filename = Path.Combine(dirPath, Path.ChangeExtension(filename, "mkv"));

pkt = ffmpeg.av_packet_alloc();
            if (pkt == null)
            {
                Console.WriteLine("Could not allocate AVPacket");
                return 1;
            }

if ((ret = ffmpeg.avformat_open_input(&amp;ifmt_ctx, in_filename, null, null)) &lt; 0)
            {
                Console.WriteLine($"Could not open input fiel '{in_filename}'");
                goto end;
            }

if ((ret = ffmpeg.avformat_find_stream_info(ifmt_ctx, null)) &lt; 0)
            {
                Console.WriteLine("Failed to retrieve input stream information");
                goto end;
            }

ffmpeg.av_dump_format(ifmt_ctx, 0, in_filename, 0);

ffmpeg.avformat_alloc_output_context2(&amp;ofmt_ctx, null, null, out_filename);
            if (ofmt_ctx == null)
            {
                Console.WriteLine("Could not create output context");
                ret = ffmpeg.AVERROR_UNKNOWN;
                goto end;
            }

stream_mapping_size = (int)ifmt_ctx-&gt;nb_streams;
            stream_mapping = (int *)ffmpeg.av_calloc((ulong)stream_mapping_size, 4);
            if (stream_mapping == null)
            {
                ret = ffmpeg.AVERROR(ffmpeg.ENOMEM);
                goto end;
            }

ofmt = ofmt_ctx-&gt;oformat;

for (i = 0; i &lt; ifmt_ctx-&gt;nb_streams; i ++)
            {
                AVStream* out_stream;
                AVStream* in_stream = ifmt_ctx-&gt;streams[i];
                AVCodecParameters* in_codecpar = in_stream-&gt;codecpar;

if (in_codecpar-&gt;codec_type != AVMediaType.AVMEDIA_TYPE_AUDIO &amp;&amp;
                    in_codecpar-&gt;codec_type != AVMediaType.AVMEDIA_TYPE_VIDEO &amp;&amp;
                    in_codecpar-&gt;codec_type != AVMediaType.AVMEDIA_TYPE_SUBTITLE)
                {
                    stream_mapping[i] = -1;
                    continue;
                }

stream_mapping[i] = stream_index++;

out_stream = ffmpeg.avformat_new_stream(ofmt_ctx, null);
                if (out_stream == null)
                {
                    Console.WriteLine("Failed allocating output stream");
                    ret = ffmpeg.AVERROR_UNKNOWN;
                    goto end;
                }

ret = ffmpeg.avcodec_parameters_copy(out_stream-&gt;codecpar, in_codecpar);
                if (ret &lt; 0)
                {
                    Console.WriteLine("Failed to copy codec parameters");
                    goto end;
                }

out_stream-&gt;codecpar-&gt;codec_tag = 0;
            }

ffmpeg.av_dump_format(ofmt_ctx, 0, out_filename, 1);

if ((ofmt-&gt;flags &amp; ffmpeg.AVFMT_NOFILE) == 0)
            {
                ret = ffmpeg.avio_open(&amp;ofmt_ctx-&gt;pb, out_filename, ffmpeg.AVIO_FLAG_WRITE);
                if (ret &lt; 0)
                {
                    Console.WriteLine($"Could not open output file '{out_filename}");
                    goto end;
                }
            }

ret = ffmpeg.avformat_write_header(ofmt_ctx, null);
            if (ret &lt; 0)
            {
                Console.WriteLine("Error occurred when opening output file");
                goto end;
            }

while (true)
            {
                AVStream* in_stream;
                AVStream* out_stream;

ret = ffmpeg.av_read_frame(ifmt_ctx, pkt);
                if (ret &lt; 0)
                {
                    break;
                }

in_stream = ifmt_ctx-&gt;streams[pkt-&gt;stream_index];
                if (pkt-&gt;stream_index &gt;= stream_mapping_size || stream_mapping[pkt-&gt;stream_index] &lt; 0)
                {
                    ffmpeg.av_packet_unref(pkt);
                    continue;
                }

pkt-&gt;stream_index = stream_mapping[pkt-&gt;stream_index];
                out_stream = ofmt_ctx-&gt;streams[pkt-&gt;stream_index];
                log_packet(ifmt_ctx, pkt, "in");

ffmpeg.av_packet_rescale_ts(pkt, in_stream-&gt;time_base, out_stream-&gt;time_base);
                pkt-&gt;pos = -1;
                log_packet(ofmt_ctx, pkt, "out");

ret = ffmpeg.av_interleaved_write_frame(ofmt_ctx, pkt);
                if (ret &lt; 0)
                {
                    Console.WriteLine("Error muxing packet");
                    break;
                }
            }

ffmpeg.av_write_trailer(ofmt_ctx);

end:
            ffmpeg.av_packet_free(&amp;pkt);
            ffmpeg.avformat_close_input(&amp;ifmt_ctx);

if (ofmt_ctx != null &amp;&amp; (ofmt-&gt;flags &amp; ffmpeg.AVFMT_NOFILE) == 0)
            {
                ffmpeg.avio_closep(&amp;ofmt_ctx-&gt;pb);
            }

ffmpeg.avformat_free_context(ofmt_ctx);

ffmpeg.av_freep(&amp;stream_mapping);

if (ret &lt; 0 &amp;&amp; ret != ffmpeg.AVERROR_EOF)
            {
                Console.WriteLine($"Error occurred: {FFmpegHelper.av_err2str(ret)}");
                return 1;
            }

return 0;
 }
 }
}
</pre>
 
몇 개의 확장자로 예제 비디오 파일을 테스트해 봤더니 avi, vob, mpeg로는 각각 다음과 같은 식의 오류가 발생했습니다. 
 
<pre style='margin: 10px 0px 10px 10px; padding: 10px 0px 10px 10px; background-color: #fbedbb; overflow: auto; font-family: Consolas, Verdana;' >
avi: 
 H.264 bitstream malformed, no startcode found, use the video bitstream filter 'h264_mp4toannexb' to fix it ('-bsf:v h264_mp4toannexb' option with ffmpeg)
 Error muxing packet
 Error occurred: Invalid data found when processing input

vob:
    [svcd @ 000001ecb820b380] VBV buffer size not set, using default size of 230KB
    If you want the mpeg file to be compliant to some specification
    Like DVD, VCD or others, make sure you set the correct buffer size
    [svcd @ 000001ecb820b380] Unsupported audio codec.Must be one of mp1, mp2, mp3, 16 - bit pcm_dvd, pcm_s16be, ac3 or dts.
    Error occurred when opening output file
    Error occurred: Invalid argument

mpeg: 
 [mpeg @ 0000020de269b380] VBV buffer size not set, using default size of 230KB
 If you want the mpeg file to be compliant to some specification
 Like DVD, VCD or others, make sure you set the correct buffer size
 [mpeg @ 0000020de269b380] Unsupported audio codec.Must be one of mp1, mp2, mp3, 16 - bit pcm_dvd, pcm_s16be, ac3 or dts.
 Error occurred when opening output file
 Error occurred: Invalid argument
</pre>
 
에러 메시지로 보아, vob와 mpeg의 경우에는 오디오 코덱을 바꾸면 될 것도 같습니다. 
 
반면, mkv, asf, mov, vob, flv, mp4, ts로는 다음과 같은 메시지와 함께 변경이 잘 되었습니다. 
 
<pre style='margin: 10px 0px 10px 10px; padding: 10px 0px 10px 10px; background-color: #fbedbb; overflow: auto; font-family: Consolas, Verdana;' >
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '...[생략]...\..\..\..\Samples\sample-10s.mp4':
 Metadata:
 major_brand : isom
 minor_version : 512
 compatible_brands: isomiso2avc1mp41
 encoder : Lavf58.44.100
 Duration: 00:00:10.24, start: 0.000000, bitrate: 4285 kb/s
 Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 4207 kb/s, 29.97 fps, 29.97 tbr, 30k tbn (default)
 Metadata:
 handler_name : VideoHandler
 vendor_id : [0][0][0][0]
 Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 121 kb/s (default)
 Metadata:
 handler_name : SoundHandler
 vendor_id : [0][0][0][0]
Output #0, mov, to '...[생략]...\sample-10s.mov':
 Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 4207 kb/s
 Stream #0:1: Audio: aac (LC), 44100 Hz, stereo, fltp, 121 kb/s
in: pts:0 pts_time:NOPTS dts:-2002 dts_time:-0.0667333 duration:1001 duration_time:0.0333667 stream_index: 0
out: pts:0 pts_time:NOPTS dts:-6006 dts_time:-0.0667333 duration:3003 duration_time:0.0333667 stream_index: 0
in: pts:4004 pts_time:0.133467 dts:-1001 dts_time:-0.0333667 duration:1001 duration_time:0.0333667 stream_index: 0
out: pts:12012 pts_time:0.133467 dts:-3003 dts_time:-0.0333667 duration:3003 duration_time:0.0333667 stream_index: 0
...[생략]...
out: pts:448512 pts_time:10.1703 dts:448512 dts_time:10.1703 duration:1024 duration_time:0.02322 stream_index: 1
in: pts:449536 pts_time:10.1936 dts:449536 dts_time:10.1936 duration:990 duration_time:0.022449 stream_index: 1
out: pts:449536 pts_time:10.1936 dts:449536 dts_time:10.1936 duration:990 duration_time:0.022449 stream_index: 1
</pre>
 
(<a target='tab' href='https://github.com/stjeong/ffmpeg_autogen_cs/tree/master/remuxing'>이 글의 소스 코드는 github에 올려</a>져 있습니다.) 
 
참고로, 다음의 글에 있는 소스 코드도 함께 보시면 좀 더 친숙할 것입니다. ^^ 
 
<pre style='margin: 10px 0px 10px 10px; padding: 10px 0px 10px 10px; background-color: #fbedbb; overflow: auto; font-family: Consolas, Verdana;' >
C# - ffmpeg(FFmpeg.AutoGen)를 이용한 demuxing_decoding.c 예제 포팅
; <a target='tab' href='https://www.sysnet.pe.kr/2/0/12987'>https://www.sysnet.pe.kr/2/0/12987</a>

C# - ffmpeg(FFmpeg.AutoGen)를 이용한 muxing.c 예제 포팅
; <a target='tab' href='https://www.sysnet.pe.kr/2/0/12971'>https://www.sysnet.pe.kr/2/0/12971</a>
</pre>

<hr />[이 글에 대해서 여러분들과 의견을 공유하고 싶습니다. 틀리거나 미흡한 부분 또는 의문 사항이 있으시면 언제든 댓글 남겨주십시오.]

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