C# - ffmpeg(FFmpeg.AutoGen)를 이용한 transcode_aac.c 예제 포팅
지난 예제에 이어,
C# - ffmpeg(FFmpeg.AutoGen)를 이용한 demuxing_decoding.c 예제 포팅
; https://www.sysnet.pe.kr/2/0/12987
이번에는
ffmpeg 예제 중 "
transcode_aac.c" 파일을 FFmpeg.AutoGen으로 포팅하겠습니다.
using FFmpeg.AutoGen;
using FFmpeg.AutoGen.Example;
using System;
using System.Diagnostics;
using System.IO;
namespace transcode_aac
{
internal unsafe class Program
{
public const int OUTPUT_BIT_RATE = 96000;
public const int OUTPUT_CHANNELS = 2;
static long pts = 0;
static unsafe int open_input_file(string filename, AVFormatContext** input_format_context,
AVCodecContext** input_codec_context)
{
AVCodecContext* avctx;
AVCodec* input_codec;
int error;
if ((error = ffmpeg.avformat_open_input(input_format_context, filename, null, null)) < 0)
{
Console.WriteLine($"Could not open input file '{filename}' (error '{FFmpegHelper.av_err2str(error)}')");
*input_format_context = null;
return error;
}
if ((error = ffmpeg.avformat_find_stream_info(*input_format_context, null)) < 0)
{
Console.WriteLine($"Could not find stream info (error '{FFmpegHelper.av_err2str(error)}')");
ffmpeg.avformat_close_input(input_format_context);
return error;
}
uint number_of_streams = (*input_format_context)->nb_streams;
if (number_of_streams != 1)
{
Console.WriteLine($"Expected one audio input stream, but found {number_of_streams}");
ffmpeg.avformat_close_input(input_format_context);
return ffmpeg.AVERROR_EXIT;
}
AVCodecParameters* codecpar = (*input_format_context)->streams[0]->codecpar;
if ((input_codec = ffmpeg.avcodec_find_decoder(codecpar->codec_id)) == null)
{
Console.WriteLine("Could not find input codec");
ffmpeg.avformat_close_input(input_format_context);
return ffmpeg.AVERROR_EXIT;
}
avctx = ffmpeg.avcodec_alloc_context3(input_codec);
if (avctx == null)
{
Console.WriteLine("Could not allocate a decoding context");
ffmpeg.avformat_close_input(input_format_context);
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
error = ffmpeg.avcodec_parameters_to_context(avctx, codecpar);
if (error < 0)
{
ffmpeg.avformat_close_input(input_format_context);
ffmpeg.avcodec_free_context(&avctx);
return error;
}
if ((error = ffmpeg.avcodec_open2(avctx, input_codec, null)) < 0)
{
Console.WriteLine($"Could not open input codec (error '{FFmpegHelper.av_err2str(error)}')");
ffmpeg.avcodec_free_context(&avctx);
ffmpeg.avformat_close_input(input_format_context);
return error;
}
*input_codec_context = avctx;
return 0;
}
static unsafe int open_output_file(string filename, AVCodecContext* input_codec_context, AVFormatContext** output_format_context,
AVCodecContext** output_codec_context)
{
AVCodecContext* avctx = null;
AVIOContext* output_io_context = null;
AVStream* stream = null;
AVCodec* output_codec = null;
int error = 0;
if ((error = ffmpeg.avio_open(&output_io_context, filename, ffmpeg.AVIO_FLAG_WRITE)) < 0)
{
Console.WriteLine($"Could not open output file '{filename}' (error '{FFmpegHelper.av_err2str(error)}')");
return error;
}
if ((*output_format_context = ffmpeg.avformat_alloc_context()) == null)
{
Console.WriteLine("Could not allocate output format context");
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
(*output_format_context)->pb = output_io_context;
if (((*output_format_context)->oformat = ffmpeg.av_guess_format(null, filename, null)) == null)
{
Console.WriteLine("Could not find output file format");
goto cleanup;
}
if (((*output_format_context)->url = ffmpeg.av_strdup(filename)) == null)
{
Console.WriteLine("Could not allocate url.");
error = ffmpeg.AVERROR(ffmpeg.ENOMEM);
goto cleanup;
}
if ((output_codec = ffmpeg.avcodec_find_encoder(AVCodecID.AV_CODEC_ID_AAC)) == null)
{
Console.WriteLine("Could not find an AAC encoder");
goto cleanup;
}
if ((stream = ffmpeg.avformat_new_stream(*output_format_context, null)) == null)
{
Console.WriteLine("Could not create new stream");
error = ffmpeg.AVERROR(ffmpeg.ENOMEM);
goto cleanup;
}
avctx = ffmpeg.avcodec_alloc_context3(output_codec);
if (avctx == null)
{
Console.WriteLine("Could not allocate an encoding context");
error = ffmpeg.AVERROR(ffmpeg.ENOMEM);
goto cleanup;
}
avctx->channels = OUTPUT_CHANNELS;
avctx->channel_layout = (ulong)ffmpeg.av_get_default_channel_layout(OUTPUT_CHANNELS);
avctx->sample_rate = input_codec_context->sample_rate;
avctx->sample_fmt = output_codec->sample_fmts[0];
avctx->bit_rate = OUTPUT_BIT_RATE;
avctx->strict_std_compliance = ffmpeg.FF_COMPLIANCE_EXPERIMENTAL;
stream->time_base.den = input_codec_context->sample_rate;
stream->time_base.num = 1;
if (((*output_format_context)->oformat->flags & ffmpeg.AVFMT_GLOBALHEADER) == ffmpeg.AVFMT_GLOBALHEADER)
{
avctx->flags |= ffmpeg.AV_CODEC_FLAG_GLOBAL_HEADER;
}
if ((error = ffmpeg.avcodec_open2(avctx, output_codec, null)) < 0)
{
Console.WriteLine($"Could not open output codec (error '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
error = ffmpeg.avcodec_parameters_from_context(stream->codecpar, avctx);
if (error < 0)
{
Console.WriteLine("Could not initialize stream parameters");
goto cleanup;
}
*output_codec_context = avctx;
return 0;
cleanup:
ffmpeg.avcodec_free_context(&avctx);
ffmpeg.avio_closep(&(*output_format_context)->pb);
ffmpeg.avformat_free_context(*output_format_context);
*output_format_context = null;
return error < 0 ? error : ffmpeg.AVERROR_EXIT;
}
static unsafe int init_packet(AVPacket** packet)
{
if ((*packet = ffmpeg.av_packet_alloc()) == null)
{
Console.WriteLine("Could not allocate packet");
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
return 0;
}
static unsafe int init_input_frame(AVFrame** frame)
{
if ((*frame = ffmpeg.av_frame_alloc()) == null)
{
Console.WriteLine("Could not allocate input frame");
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
return 0;
}
static unsafe int init_resampler(AVCodecContext* input_codec_context, AVCodecContext* output_codec_context,
SwrContext** resample_context)
{
int error = 0;
*resample_context = ffmpeg.swr_alloc_set_opts(null,
ffmpeg.av_get_default_channel_layout(output_codec_context->channels),
output_codec_context->sample_fmt,
output_codec_context->sample_rate,
ffmpeg.av_get_default_channel_layout(input_codec_context->channels),
input_codec_context->sample_fmt,
input_codec_context->sample_rate,
0, null);
if (*resample_context == null)
{
Console.WriteLine("Could not allocate resample context");
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
Trace.Assert(output_codec_context->sample_rate == input_codec_context->sample_rate);
if ((error = ffmpeg.swr_init(*resample_context)) < 0)
{
Console.WriteLine("Could not open resample context");
ffmpeg.swr_free(resample_context);
return error;
}
return 0;
}
static unsafe int init_fifo(AVAudioFifo** fifo, AVCodecContext* output_codec_context)
{
if ((*fifo = ffmpeg.av_audio_fifo_alloc(output_codec_context->sample_fmt, output_codec_context->channels, 1)) == null)
{
Console.WriteLine("Could not allocate FIFO");
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
return 0;
}
static unsafe int write_output_file_header(AVFormatContext* output_format_context)
{
int error = ffmpeg.avformat_write_header(output_format_context, null);
if (error < 0)
{
Console.WriteLine($"Could not write output file header (error '{FFmpegHelper.av_err2str(error)}'");
return error;
}
return 0;
}
static unsafe int decode_audio_frame(AVFrame* frame, AVFormatContext* input_format_context, AVCodecContext* input_codec_context,
int* data_present, int* finished)
{
AVPacket* input_packet;
int error = init_packet(&input_packet);
if (error < 0)
{
return error;
}
if ((error = ffmpeg.av_read_frame(input_format_context, input_packet)) < 0)
{
if (error == ffmpeg.AVERROR_EOF)
{
*finished = 1;
}
else
{
Console.WriteLine($"Could not raed frame (eror '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
}
if ((error = ffmpeg.avcodec_send_packet(input_codec_context, input_packet)) < 0)
{
Console.WriteLine($"Could not send packet for decoding (error '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
error = ffmpeg.avcodec_receive_frame(input_codec_context, frame);
if (error == ffmpeg.AVERROR(ffmpeg.EAGAIN))
{
error = 0;
goto cleanup;
}
else if (error == ffmpeg.AVERROR_EOF)
{
*finished = 1;
error = 0;
goto cleanup;
}
else if (error < 0)
{
Console.WriteLine($"Could not decode frame (error '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
else
{
*data_present = 1;
goto cleanup;
}
cleanup:
ffmpeg.av_packet_free(&input_packet);
return error;
}
static unsafe int init_converted_samples(byte*** converted_input_samples, AVCodecContext* output_codec_context, int frame_size)
{
if ((*converted_input_samples = (byte**)ffmpeg.av_calloc((ulong)output_codec_context->channels, (ulong)IntPtr.Size)) == null)
{
Console.WriteLine("Could not allocate converted input sample pointers");
return ffmpeg.AVERROR(ffmpeg.ENOMEM);
}
int error = ffmpeg.av_samples_alloc(*converted_input_samples, null, output_codec_context->channels, frame_size, output_codec_context->sample_fmt, 0);
if (error < 0)
{
Console.WriteLine($"Could not allocate converted input samples (error '{FFmpegHelper.av_err2str(error)}')");
ffmpeg.av_freep(&(*converted_input_samples)[0]);
ffmpeg.av_free(*converted_input_samples);
return error;
}
return 0;
}
static unsafe int converted_samples(byte** input_data, byte** converted_data, int frame_size, SwrContext* resample_context)
{
int error = ffmpeg.swr_convert(resample_context, converted_data, frame_size, input_data, frame_size);
if (error < 0)
{
Console.WriteLine($"Could not convert input samples (error '{FFmpegHelper.av_err2str(error)}')");
return error;
}
return 0;
}
static unsafe int add_samples_to_fifo(AVAudioFifo* fifo, byte** converted_input_samples, int frame_size)
{
int error = ffmpeg.av_audio_fifo_realloc(fifo, ffmpeg.av_audio_fifo_size(fifo) + frame_size);
if (error < 0)
{
Console.WriteLine("Could not reallocate FIFO");
return error;
}
if (ffmpeg.av_audio_fifo_write(fifo, (void**)converted_input_samples, frame_size) < frame_size)
{
Console.WriteLine("Could not write data to FIFO");
return ffmpeg.AVERROR_EXIT;
}
return 0;
}
static unsafe int read_decode_convert_and_store(AVAudioFifo* fifo,
AVFormatContext* input_format_context, AVCodecContext* input_codec_context,
AVCodecContext* output_codec_context, SwrContext* resampler_context, int* finished)
{
AVFrame* input_frame = null;
byte** converted_input_samples = null;
int data_present = 0;
int ret = ffmpeg.AVERROR_EXIT;
if (init_input_frame(&input_frame) != 0)
{
goto cleanup;
}
if (decode_audio_frame(input_frame, input_format_context, input_codec_context, &data_present, finished) != 0)
{
goto cleanup;
}
if (*finished != 0)
{
ret = 0;
goto cleanup;
}
if (data_present != 0)
{
if (init_converted_samples(&converted_input_samples, output_codec_context, input_frame->nb_samples) != 0)
{
goto cleanup;
}
if (converted_samples(input_frame->extended_data, converted_input_samples, input_frame->nb_samples, resampler_context) != 0)
{
goto cleanup;
}
if (add_samples_to_fifo(fifo, converted_input_samples, input_frame->nb_samples) != 0)
{
goto cleanup;
}
ret = 0;
}
ret = 0;
cleanup:
if (converted_input_samples != null)
{
ffmpeg.av_freep(&converted_input_samples[0]);
ffmpeg.av_free(converted_input_samples);
}
ffmpeg.av_frame_free(&input_frame);
return ret;
}
static unsafe int init_output_frame(AVFrame** frame, AVCodecContext* output_codec_context, int frame_size)
{
int error;
if ((*frame = ffmpeg.av_frame_alloc()) == null)
{
Console.WriteLine("Could not allocate output frame");
return ffmpeg.AVERROR_EXIT;
}
(*frame)->nb_samples = frame_size;
(*frame)->channel_layout = output_codec_context->channel_layout;
(*frame)->format = (int)output_codec_context->sample_fmt;
(*frame)->sample_rate = output_codec_context->sample_rate;
if ((error = ffmpeg.av_frame_get_buffer(*frame, 0)) < 0)
{
Console.WriteLine($"Could not allocate output frame samples (error '{FFmpegHelper.av_err2str(error)}')");
ffmpeg.av_frame_free(frame);
return error;
}
return 0;
}
static unsafe int encode_audio_frame(AVFrame* frame, AVFormatContext* output_format_context, AVCodecContext* output_codec_context, int* data_present)
{
AVPacket* output_packet;
int error = init_packet(&output_packet);
if (error < 0)
{
return error;
}
if (frame != null)
{
frame->pts = pts;
pts += frame->nb_samples;
}
error = ffmpeg.avcodec_send_frame(output_codec_context, frame);
if (error == ffmpeg.AVERROR_EOF)
{
error = 0;
goto cleanup;
}
else if (error < 0)
{
Console.WriteLine($"Could not send packet for encoding (error '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
error = ffmpeg.avcodec_receive_packet(output_codec_context, output_packet);
if (error == ffmpeg.AVERROR(ffmpeg.EAGAIN))
{
error = 0;
goto cleanup;
}
else if (error == ffmpeg.AVERROR_EOF)
{
error = 0;
goto cleanup;
}
else if (error < 0)
{
Console.WriteLine($"Could not encode frame (error '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
else
{
*data_present = 1;
}
if (*data_present != 0 &&
(error = ffmpeg.av_write_frame(output_format_context, output_packet)) < 0)
{
Console.WriteLine($"Could not write frame (error '{FFmpegHelper.av_err2str(error)}')");
goto cleanup;
}
cleanup:
ffmpeg.av_packet_free(&output_packet);
return error;
}
static unsafe int load_encode_and_write(AVAudioFifo* fifo, AVFormatContext* output_format_context,
AVCodecContext* output_codec_context)
{
AVFrame* output_frame;
int frame_size = Math.Min(ffmpeg.av_audio_fifo_size(fifo), output_codec_context->frame_size);
int data_written;
if (init_output_frame(&output_frame, output_codec_context, frame_size) != 0)
{
return ffmpeg.AVERROR_EXIT;
}
void* ptr = &output_frame->data;
if (ffmpeg.av_audio_fifo_read(fifo, (void**)ptr, frame_size) < frame_size)
{
ffmpeg.av_frame_free(&output_frame);
return ffmpeg.AVERROR_EXIT;
}
if (encode_audio_frame(output_frame, output_format_context, output_codec_context, &data_written) != 0)
{
ffmpeg.av_frame_free(&output_frame);
return ffmpeg.AVERROR_EXIT;
}
ffmpeg.av_frame_free(&output_frame);
return 0;
}
static unsafe int write_output_file_trailer(AVFormatContext* output_format_context)
{
int error = ffmpeg.av_write_trailer(output_format_context);
if (error < 0)
{
Console.WriteLine($"Could not write output file trailer (error '{FFmpegHelper.av_err2str(error)}')");
return error;
}
return 0;
}
static unsafe int Main(string[] args)
{
FFmpegBinariesHelper.RegisterFFmpegBinaries();
#if DEBUG
Console.WriteLine("Current directory: " + Environment.CurrentDirectory);
Console.WriteLine("Running in {0}-bit mode.", Environment.Is64BitProcess ? "64" : "32");
Console.WriteLine($"FFmpeg version info: {ffmpeg.av_version_info()}");
Console.WriteLine();
#endif
AVFormatContext* input_format_context = null;
AVFormatContext* output_format_context = null;
AVCodecContext* input_codec_conetxt = null;
AVCodecContext* output_codec_conetxt = null;
SwrContext* resample_context = null;
AVAudioFifo* fifo = null;
int ret = ffmpeg.AVERROR_EXIT;
string dirPath = Path.GetDirectoryName(typeof(Program).Assembly.Location) ?? "";
// https://samplelib.com/sample-mp3.html
string input_file_path = Path.Combine(dirPath, "..", "..", "..", "Samples", "sample-12s.mp3");
string output_file_path = Path.Combine(dirPath, "output.aac");
if (open_input_file(input_file_path, &input_format_context, &input_codec_conetxt) != 0)
{
goto cleanup;
}
if (open_output_file(output_file_path, input_codec_conetxt, &output_format_context, &output_codec_conetxt) != 0)
{
goto cleanup;
}
if (init_resampler(input_codec_conetxt, output_codec_conetxt, &resample_context) != 0)
{
goto cleanup;
}
if (init_fifo(&fifo, output_codec_conetxt) != 0)
{
goto cleanup;
}
if (write_output_file_header(output_format_context) != 0)
{
goto cleanup;
}
while (true)
{
int output_frame_size = output_codec_conetxt->frame_size;
int finished = 0;
while (ffmpeg.av_audio_fifo_size(fifo) < output_frame_size)
{
if (read_decode_convert_and_store(fifo, input_format_context, input_codec_conetxt, output_codec_conetxt,
resample_context, &finished) != 0)
{
goto cleanup;
}
if (finished != 0)
{
break;
}
}
while (ffmpeg.av_audio_fifo_size(fifo) >= output_frame_size
|| (finished != 0 && ffmpeg.av_audio_fifo_size(fifo) > 0))
{
if (load_encode_and_write(fifo, output_format_context, output_codec_conetxt) != 0)
{
goto cleanup;
}
}
if (finished != 0)
{
int data_written;
do
{
data_written = 0;
if (encode_audio_frame(null, output_format_context, output_codec_conetxt, &data_written) != 0)
{
goto cleanup;
}
} while (data_written != 0);
break;
}
}
if (write_output_file_trailer(output_format_context) != 0)
{
goto cleanup;
}
ret = 0;
cleanup:
if (fifo != null)
{
ffmpeg.av_audio_fifo_free(fifo);
}
ffmpeg.swr_free(&resample_context);
if (output_codec_conetxt != null)
{
ffmpeg.avio_closep(&output_format_context->pb);
ffmpeg.avformat_free_context(output_format_context);
}
if (input_codec_conetxt != null)
{
ffmpeg.avcodec_free_context(&input_codec_conetxt);
}
if (input_format_context != null)
{
ffmpeg.avformat_close_input(&input_format_context);
}
return ret;
}
}
}
"
transcode_aac.c" 링크의 소개에 위의 코드가 어떤 동작을 하는지 개략적으로 소개하고 있습니다.
Convert an input audio file to AAC in an MP4 container using FFmpeg.Formats other than MP4 are supported based on the output file extension.
간단하게 테스트를 한다면, mp3 파일을 입력으로,
c:\temp> ffprobe "C:\Samples\sample-12s.mp3"
...[생략]...
Input #0, mp3, from 'C:\Samples\sample-12s.mp3':
Metadata:
encoder : Lavf57.83.100
Duration: 00:00:12.83, start: 0.025057, bitrate: 128 kb/s
Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 128 kb/s
Metadata:
encoder : Lavc57.10
실행하면 "output.aac" 파일이 생성됩니다.
c:\temp> ffprobe output.aac
...[생략]...
[aac @ 00000200D14EC7C0] Estimating duration from bitrate, this may be inaccurate
Input #0, aac, from 'output.aac':
Duration: 00:00:12.68, bitrate: 98 kb/s
Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp, 98 kb/s
생성된 output.aac 파일은 ffplay뿐만 아니라 일반적인 윈도우 미디어 플레이어로도 잘 재생됩니다.
(
이 글의 소스 코드는 github에 올려져 있습니다.)
[이 글에 대해서 여러분들과 의견을 공유하고 싶습니다. 틀리거나 미흡한 부분 또는 의문 사항이 있으시면 언제든 댓글 남겨주십시오.]