将内容翻译为中文： 写入到ffpmeg的标准输入会导致程序冻结。

huangapple
go评论120阅读模式
英文:

Writing to ffpmeg stdin freezes program

问题

我正在尝试使用ffmpeg将内存中的文件转换为另一种格式，通过使用stdin和stdout，但每次我尝试写入stdin时，我的ffmpeg命令就会卡住。

  1. package main
  3. import (
  4. 	"bufio"
  5. 	"fmt"
  6. 	"io"
  7. 	"os"
  8. 	"os/exec"
  9. )
  11. func test(bytes []byte) ([]byte, error) {
  13. 	cmd := exec.Command(
  14. 		"ffmpeg",
  15. 		"-i", "pipe:0", // 从stdin读取
  16. 		"-vcodec", "copy",
  17. 		"-acodec", "copy",
  18. 		"-f", "matroska",
  19. 		"pipe:1",
  20. 	)
  22. 	in, err := cmd.StdinPipe()
  23. 	if err != nil {
  24. 		panic(err)
  25. 	}
  26. 	out, err := cmd.StdoutPipe()
  27. 	if err != nil {
  28. 		panic(err)
  29. 	}
  31. 	fmt.Println("starting")
  32. 	err = cmd.Start()
  33. 	if err != nil {
  34. 		panic(err)
  35. 	}
  37. 	fmt.Println("writing")
  38. 	w := bufio.NewWriter(in)
  39. 	_, err = w.Write(bytes)
  40. 	if err != nil {
  41. 		panic(err)
  42. 	}
  44. 	err = w.Flush()
  45. 	if err != nil {
  46. 		panic(err)
  47. 	}
  49. 	err = in.Close()
  50. 	if err != nil {
  51. 		panic(err)
  52. 	}
  54. 	fmt.Println("reading")
  55. 	outBytes, err := io.ReadAll(out)
  56. 	if err != nil {
  57. 		panic(err)
  58. 	}
  60. 	fmt.Println("waiting")
  61. 	err = cmd.Wait()
  62. 	if err != nil {
  63. 		panic(err)
  64. 	}
  66. 	return outBytes, nil
  67. }
  69. func main() {
  70. 	dat, err := os.ReadFile("speech.mp4")
  71. 	if err != nil {
  72. 		panic(err)
  73. 	}
  75. 	out, err := test(dat)
  76. 	if err != nil {
  77. 		panic(err)
  78. 	}
  80. 	err = os.WriteFile("test.m4v", out, 0644)
  81. 	if err != nil {
  82. 		panic(err)
  83. 	}
  84. }

它打印出：

  1. starting
  2. writing

然后卡住了。我尝试使用grep运行类似的代码，一切正常工作，所以这似乎是一些特定于ffmpeg的问题。

我尝试运行：

cat speech.mp4 | ffmpeg -i pipe:0 -vcodec copy -acodec copy -f matroska pipe:1 | cat > test.mkv

这个命令可以正常工作，所以不是ffmpeg的问题，而是我在处理数据的方式上出了问题。

我的speech.mp4文件大小约为2MB。

英文:

I'm trying to convert a file in memory using ffmpeg to another format by using stdin and stdout, but everytime I try to write to stdin, of my ffmpeg command, it just freezes there.

  1. package main
  3. import (
  4. 	"bufio"
  5. 	"fmt"
  6. 	"io"
  7. 	"os"
  8. 	"os/exec"
  9. )
  11. func test(bytes []byte) ([]byte, error) {
  13. 	cmd := exec.Command(
  14. 		"ffmpeg",
  15. 		"-i", "pipe:0", // read from stdin
  16. 		"-vcodec", "copy",
  17. 		"-acodec", "copy",
  18. 		"-f", "matroska",
  19. 		"pipe:1",
  20. 	)
  22. 	in, err := cmd.StdinPipe()
  23. 	if err != nil {
  24. 		panic(err)
  25. 	}
  26. 	out, err := cmd.StdoutPipe()
  27. 	if err != nil {
  28. 		panic(err)
  29. 	}
  31. 	fmt.Println("starting")
  32. 	err = cmd.Start()
  33. 	if err != nil {
  34. 		panic(err)
  35. 	}
  37. 	fmt.Println("writing")
  38. 	w := bufio.NewWriter(in)
  39. 	_, err = w.Write(bytes)
  40. 	if err != nil {
  41. 		panic(err)
  42. 	}
  44. 	err = w.Flush()
  45. 	if err != nil {
  46. 		panic(err)
  47. 	}
  49. 	err = in.Close()
  50. 	if err != nil {
  51. 		panic(err)
  52. 	}
  54. 	fmt.Println("reading")
  55. 	outBytes, err := io.ReadAll(out)
  56. 	if err != nil {
  57. 		panic(err)
  58. 	}
  60. 	fmt.Println("waiting")
  61. 	err = cmd.Wait()
  62. 	if err != nil {
  63. 		panic(err)
  64. 	}
  66. 	return outBytes, nil
  67. }
  69. func main() {
  70. 	dat, err := os.ReadFile("speech.mp4")
  71. 	if err != nil {
  72. 		panic(err)
  73. 	}
  75. 	out, err := test(dat)
  76. 	if err != nil {
  77. 		panic(err)
  78. 	}
  80. 	err = os.WriteFile("test.m4v", out, 0644)
  81. 	if err != nil {
  82. 		panic(err)
  83. 	}
  84. }

It prints

  1. starting
  2. writing

and gets stuck there. I tried similar code with grep, and the everything worked fine, so this seems to be some ffmpeg specific problem.

I tried running

cat speech.mp4 | ffmpeg -i pipe:0 -vcodec copy -acodec copy -f matroska pipe:1 | cat > test.mkv

and that works fine, so it's not an ffmpeg problem, but some problem with how I'm piping/reading/writing my data.

My speech.mp4 file is around 2MB.

答案1

得分: 1

所以秘密就在于在将字节转储到stdin时读取stdout，因为写入管道会阻塞。感谢@JimB帮助我找出这个问题。

你只需要在写入时进行读取：

  1. cmd := exec.Command(
  2. 	"ffmpeg",
  3. 	"-i", "pipe:0", // 从stdin读取
  4. 	"-vcodec", "copy",
  5. 	"-acodec", "copy",
  6. 	"-f", "matroska",
  7. 	"pipe:1",
  8. )
  10. out, err := cmd.StdoutPipe()
  11. if err != nil {
  12. 	panic(err)
  13. }
  15. in, err := cmd.StdinPipe()
  16. writer := bufio.NewWriter(in)
  17. if err != nil {
  18. 	panic(err)
  19. }
  21. fmt.Println("开始")
  22. err = cmd.Start()
  23. if err != nil {
  24. 	panic(err)
  25. }
  27. go func() {
  28. 	defer writer.Flush()
  29. 	defer in.Close()
  30. 	fmt.Println("写入")
  31. 	_, err = writer.Write(bytes)
  32. 	if err != nil {
  33. 		panic(err)
  34. 	}
  35. }()
  37. var outBytes []byte
  39. defer out.Close()
  40. fmt.Println("读取")
  41. outBytes, err = io.ReadAll(out)
  42. if err != nil {
  43. 	panic(err)
  44. }
  45. fmt.Println("等待")
  46. err = cmd.Wait()
  47. if err != nil {
  48. 	panic(err)
  49. }
  51. return outBytes, nil
英文:

So the secret lied in reading stdout as you dumped the bytes into stdin, since writing to the pipe blocks. Thanks @JimB for helping me figure this out.

You just have to read as you write:

  1. cmd := exec.Command(
  2. 	"ffmpeg",
  3. 	"-i", "pipe:0", // read from stdin
  4. 	"-vcodec", "copy",
  5. 	"-acodec", "copy",
  6. 	"-f", "matroska",
  7. 	"pipe:1",
  8. )
  10. out, err := cmd.StdoutPipe()
  11. if err != nil {
  12. 	panic(err)
  13. }
  15. in, err := cmd.StdinPipe()
  16. writer := bufio.NewWriter(in)
  17. if err != nil {
  18. 	panic(err)
  19. }
  21. fmt.Println("starting")
  22. err = cmd.Start()
  23. if err != nil {
  24. 	panic(err)
  25. }
  27. go func() {
  28. 	defer writer.Flush()
  29. 	defer in.Close()
  30. 	fmt.Println("writing")
  31. 	_, err = writer.Write(bytes)
  32. 	if err != nil {
  33. 		panic(err)
  34. 	}
  35. }()
  37. var outBytes []byte
  39. defer out.Close()
  40. fmt.Println("reading")
  41. outBytes, err = io.ReadAll(out)
  42. if err != nil {
  43. 	panic(err)
  44. }
  45. fmt.Println("waiting")
  46. err = cmd.Wait()
  47. if err != nil {
  48. 	panic(err)
  49. }
  51. return outBytes, nil

huangapple
  • 本文由 发表于 2021年12月24日 02:28:24
  • 转载请务必保留本文链接：https://go.coder-hub.com/70466094.html
  • ffmpeg
  • go
  • stdin
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