Problems with calling ffmpeg on linux to record video with a camera

[jianwt]

I want to use ffmpeg on linux to record video with the camera on my laptop and save the video as MP4 format. ffmpeg has been deployed in linux system, the camera can be identified by ffmpeg, also obtained the "DEV" permission, but only support "yuyv", video input device is "/dev/video0", the following code debugging for a long time can not save the video recording in the camera to the local. Please look at the code, thank you very much!

Code: Pascal  [Select][+][-]

1.  
2. unit Unit1;
3.  
4. {$mode objfpc}{$H+}
5.  
6. interface
7.  
8. uses
9.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls, Process, Unix;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     btnStart: TButton;
17.     btnStop: TButton;
18.     Memo1: TMemo;
19.     SaveDialog1: TSaveDialog;
20.     procedure btnStartClick(Sender: TObject);
21.     procedure btnStopClick(Sender: TObject);
22.     procedure FormCreate(Sender: TObject);
23.   private
24.   FRecording: Boolean;
25.     FFmpegProcess: TProcess;
26.   public
27.          procedure StartRecording(const FileName: string);
28.     procedure StopRecording;
29.   end;
30.  
31. var
32.   Form1: TForm1;
33.  
34. implementation
35.  
36. {$R *.lfm}
37.  
38. { TForm1 }
39.  
40. procedure TForm1.FormCreate(Sender: TObject);
41. begin
42.     btnStop.Enabled := False;
43.   FRecording := False;
44. end;
45.  
46. procedure TForm1.btnStartClick(Sender: TObject);
47. var
48.   VideoDevice, AudioDevice: string;
49. begin
50.   if SaveDialog1.Execute then
51.   begin
52.  
53.     VideoDevice := '/dev/video0';
54.     AudioDevice := 'hw:0';
55.  
56.     if not FileExists(VideoDevice) then
57.     begin
58.       ShowMessage('视频设备不存在: ' + VideoDevice);
59.       Exit;
60.     end;
61.  
62.     StartRecording(SaveDialog1.FileName);
63.     btnStart.Enabled := False;
64.     btnStop.Enabled := True;
65.     FRecording := True;
66.   end;
67. end;
68.  
69. procedure TForm1.btnStopClick(Sender: TObject);
70. begin
71.    StopRecording;
72. end;
73.  
74. procedure TForm1.StartRecording(const FileName: string);
75. var
76.   FfmpegCmd: string;
77. begin
78.   FFmpegProcess := TProcess.Create(nil);
79.   FFmpegProcess.Executable := 'ffmpeg';
80.   FFmpegProcess.Parameters.Add('-y');
81.   FFmpegProcess.Parameters.Add('-f');
82.   FFmpegProcess.Parameters.Add('v4l2');
83.   FFmpegProcess.Parameters.Add('-input_format');
84.    FFmpegProcess.Parameters.Add('yuyv422');
85.  // FFmpegProcess.Parameters.Add('mjpeg');
86.   FFmpegProcess.Parameters.Add('-i');
87.   FFmpegProcess.Parameters.Add('/dev/video0');  // 视频输入设备
88.  
89.   // 添加音频输入（ALSA）
90.   FFmpegProcess.Parameters.Add('-f');
91.   FFmpegProcess.Parameters.Add('alsa');
92.   FFmpegProcess.Parameters.Add('-i');
93.   FFmpegProcess.Parameters.Add('hw:0');         // 音频输入设备
94.  
95.   // 设置编码参数
96.   FFmpegProcess.Parameters.Add('-c:v');
97.   FFmpegProcess.Parameters.Add('libx264');
98.   FFmpegProcess.Parameters.Add('-preset');
99.   FFmpegProcess.Parameters.Add('fast');
100.   FFmpegProcess.Parameters.Add('-c:a');
101.   FFmpegProcess.Parameters.Add('aac');
102.  
103.   // 输出文件
104.   FFmpegProcess.Parameters.Add(FileName);    //.mp4
105.  
106.   FFmpegProcess.Options := [poUsePipes, poNoConsole];
107.   FFmpegProcess.Execute;
108. end;
109.  
110. procedure TForm1.StopRecording;
111. begin
112.   if FRecording and Assigned(FFmpegProcess) then
113.   begin
114.     try
115.  
116.       FFmpegProcess.Terminate(0);
117.  
118.      // FFmpegProcess.Write('q' + LineEnding, 1 + Length(LineEnding));
119.       FFmpegProcess.WaitOnExit;
120.  
121.       if FFmpegProcess.ExitStatus = 0 then
122.         ShowMessage('录制成功！')
123.       else
124.         ShowMessage('录制失败：' + IntToStr(FFmpegProcess.ExitStatus));
125.     except
126.       on E: Exception do
127.       begin
128.         ShowMessage('停止录制时出错: ' + E.Message);
129.       end;
130.     end;
131.  
132.     FreeAndNil(FFmpegProcess);
133.     btnStart.Enabled := True;
134.     btnStop.Enabled := False;
135.     FRecording := False;
136.   end;
137. end;
138. end.        
139.  
140.  

[d2010]

Hii.
Please how to read -volume and make animation
     with Read-Volume-Level ?
or
 Play Wav with Tee-Char-Animation bellow?

[TRon]

@jianwt:
Do the parameters work as expected when you manually invoke ffmpeg from the command-line (not using Lazarus/FPC at all) ? e.g. does ffmpeg then work as expected ?

ffmpeg can be quite quirky with its parameters, especially when using TProcess parameters and/or runcommand.

[jianwt]

@jianwt:
Do the parameters work as expected when you manually invoke ffmpeg from the command-line (not using Lazarus/FPC at all) ? e.g. does ffmpeg then work as expected ?

ffmpeg can be quite quirky with its parameters, especially when using TProcess parameters and/or runcommand.

I really do not know how the "TProcess parameter" runs, so I have not figured out this thing. I have implemented the real-time display of camera content with TImage in "Lazarus/FPC", so I think it is possible to record videos and save them locally with the same principle, but my efforts cannot.

So, please understand the friends to help solve this problem, thank you.

[TRon]

Yes, I understand @jianwt but if you are not able to provide an answer to the question if ffpmeg works as expected from the terminal when using those parameters then I am not able to help.

I do not have the same setup to be able to verify and it is quite a waste of time to pursue something that perhaps does not even work in the first place.

You should at least be able to verify if ffmpeg is capable of accepting all these parameters as expected (to be sure: not by using FPC/Lazarus but only using the terminal/prompt).