ffmpeg实现音频resample(重采样)

迷南。 2022-07-11 11:25 547阅读 0赞

[下面代码是实现将音频的三大要素：声道，样本，采样率变更的demo][demo]

[例如双声道变成单声道，44100->48000，float->s16等等。 ][demo]

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][demo]

[**\[cpp\]** view plain copy][demo]

[ ![在CODE上查看代码片][CODE]![派生到我的代码片][ico_fork.svg]][demo]

1.  [**int** AudioResampling(AVCodecContext \* audio\_dec\_ctx,AVFrame \* pAudioDecodeFrame, ][demo]
2.  [ **int** out\_sample\_fmt,**int** out\_channels ,**int** out\_sample\_rate , uint8\_t \* out\_buf) ][demo]
3.  [\{ ][demo]
4.  [ //][demo]
5.  [ SwrContext \* swr\_ctx = NULL; ][demo]
6.  [ **int** data\_size = 0; ][demo]
7.  [ **int** ret = 0; ][demo]
8.  [ int64\_t src\_ch\_layout = AV\_CH\_LAYOUT\_STEREO; //初始化这样根据不同文件做调整][demo]
9.  [ int64\_t dst\_ch\_layout = AV\_CH\_LAYOUT\_STEREO; //这里设定ok][demo]
10. [ **int** dst\_nb\_channels = 0; ][demo]
11. [ **int** dst\_linesize = 0; ][demo]
12. [ **int** src\_nb\_samples = 0; ][demo]
13. [ **int** dst\_nb\_samples = 0; ][demo]
14. [ **int** max\_dst\_nb\_samples = 0; ][demo]
15. [ uint8\_t \*\*dst\_data = NULL; ][demo]
16. [ **int** resampled\_data\_size = 0; ][demo]
17. [ ][demo]
18. [ //重新采样][demo]
19. [ **if** (swr\_ctx) ][demo]
20. [ \{ ][demo]
21. [ swr\_free(&swr\_ctx); ][demo]
22. [ \} ][demo]
23. [ swr\_ctx = swr\_alloc(); ][demo]
24. [ **if** (!swr\_ctx) ][demo]
25. [ \{ ][demo]
26. [ printf("swr\_alloc error \\n"); ][demo]
27. [ **return** \-1; ][demo]
28. [ \} ][demo]
29. [ ][demo]
30. [ src\_ch\_layout = (audio\_dec\_ctx->channel\_layout && ][demo]
31. [ audio\_dec\_ctx->channels == ][demo]
32. [ av\_get\_channel\_layout\_nb\_channels(audio\_dec\_ctx->channel\_layout)) ? ][demo]
33. [ audio\_dec\_ctx->channel\_layout : ][demo]
34. [ av\_get\_default\_channel\_layout(audio\_dec\_ctx->channels); ][demo]
35. [ ][demo]
36. [ **if** (out\_channels == 1) ][demo]
37. [ \{ ][demo]
38. [ dst\_ch\_layout = AV\_CH\_LAYOUT\_MONO; ][demo]
39. [ \} ][demo]
40. [ **else****if**(out\_channels == 2) ][demo]
41. [ \{ ][demo]
42. [ dst\_ch\_layout = AV\_CH\_LAYOUT\_STEREO; ][demo]
43. [ \} ][demo]
44. [ **else**][demo]
45. [ \{ ][demo]
46. [ //可扩展][demo]
47. [ \} ][demo]
48. [ ][demo]
49. [ **if** (src\_ch\_layout <= 0) ][demo]
50. [ \{ ][demo]
51. [ printf("src\_ch\_layout error \\n"); ][demo]
52. [ **return** \-1; ][demo]
53. [ \} ][demo]
54. [ ][demo]
55. [ src\_nb\_samples = pAudioDecodeFrame->nb\_samples; ][demo]
56. [ **if** (src\_nb\_samples <= 0) ][demo]
57. [ \{ ][demo]
58. [ printf("src\_nb\_samples error \\n"); ][demo]
59. [ **return** \-1; ][demo]
60. [ \} ][demo]
61. [ ][demo]
62. [ /\* set options \*/][demo]
63. [ av\_opt\_set\_int(swr\_ctx, "in\_channel\_layout", src\_ch\_layout, 0); ][demo]
64. [ av\_opt\_set\_int(swr\_ctx, "in\_sample\_rate", audio\_dec\_ctx->sample\_rate, 0); ][demo]
65. [ av\_opt\_set\_sample\_fmt(swr\_ctx, "in\_sample\_fmt", audio\_dec\_ctx->sample\_fmt, 0); ][demo]
66. [ ][demo]
67. [ av\_opt\_set\_int(swr\_ctx, "out\_channel\_layout", dst\_ch\_layout, 0); ][demo]
68. [ av\_opt\_set\_int(swr\_ctx, "out\_sample\_rate", out\_sample\_rate, 0); ][demo]
69. [ av\_opt\_set\_sample\_fmt(swr\_ctx, "out\_sample\_fmt", (AVSampleFormat)out\_sample\_fmt, 0); ][demo]
70. [ swr\_init(swr\_ctx); ][demo]
71. [ ][demo]
72. [ max\_dst\_nb\_samples = dst\_nb\_samples = ][demo]
73. [ av\_rescale\_rnd(src\_nb\_samples, out\_sample\_rate, audio\_dec\_ctx->sample\_rate, AV\_ROUND\_UP); ][demo]
74. [ **if** (max\_dst\_nb\_samples <= 0) ][demo]
75. [ \{ ][demo]
76. [ printf("av\_rescale\_rnd error \\n"); ][demo]
77. [ **return** \-1; ][demo]
78. [ \} ][demo]
79. [ ][demo]
80. [ dst\_nb\_channels = av\_get\_channel\_layout\_nb\_channels(dst\_ch\_layout); ][demo]
81. [ ret = av\_samples\_alloc\_array\_and\_samples(&dst\_data, &dst\_linesize, dst\_nb\_channels, ][demo]
82. [ dst\_nb\_samples, (AVSampleFormat)out\_sample\_fmt, 0); ][demo]
83. [ **if** (ret < 0) ][demo]
84. [ \{ ][demo]
85. [ printf("av\_samples\_alloc\_array\_and\_samples error \\n"); ][demo]
86. [ **return** \-1; ][demo]
87. [ \} ][demo]
88. [ ][demo]
89. [ ][demo]
90. [ dst\_nb\_samples = av\_rescale\_rnd(swr\_get\_delay(swr\_ctx, audio\_dec\_ctx->sample\_rate) + ][demo]
91. [ src\_nb\_samples, out\_sample\_rate, audio\_dec\_ctx->sample\_rate,AV\_ROUND\_UP); ][demo]
92. [ **if** (dst\_nb\_samples <= 0) ][demo]
93. [ \{ ][demo]
94. [ printf("av\_rescale\_rnd error \\n"); ][demo]
95. [ **return** \-1; ][demo]
96. [ \} ][demo]
97. [ **if** (dst\_nb\_samples > max\_dst\_nb\_samples) ][demo]
98. [ \{ ][demo]
99. [ av\_free(dst\_data\[0\]); ][demo]
100. [ ret = av\_samples\_alloc(dst\_data, &dst\_linesize, dst\_nb\_channels, ][demo]
101. [ dst\_nb\_samples, (AVSampleFormat)out\_sample\_fmt, 1); ][demo]
102. [ max\_dst\_nb\_samples = dst\_nb\_samples; ][demo]
103. [ \} ][demo]
104. [ ][demo]
105. [ data\_size = av\_samples\_get\_buffer\_size(NULL, audio\_dec\_ctx->channels, ][demo]
106. [ pAudioDecodeFrame->nb\_samples, ][demo]
107. [ audio\_dec\_ctx->sample\_fmt, 1); ][demo]
108. [ **if** (data\_size <= 0) ][demo]
109. [ \{ ][demo]
110. [ printf("av\_samples\_get\_buffer\_size error \\n"); ][demo]
111. [ **return** \-1; ][demo]
112. [ \} ][demo]
113. [ resampled\_data\_size = data\_size; ][demo]
114. [ ][demo]
115. [ **if** (swr\_ctx) ][demo]
116. [ \{ ][demo]
117. [ ret = swr\_convert(swr\_ctx, dst\_data, dst\_nb\_samples, ][demo]
118. [ (**const** uint8\_t \*\*)pAudioDecodeFrame->data, pAudioDecodeFrame->nb\_samples); ][demo]
119. [ **if** (ret <= 0) ][demo]
120. [ \{ ][demo]
121. [ printf("swr\_convert error \\n"); ][demo]
122. [ **return** \-1; ][demo]
123. [ \} ][demo]
124. [ ][demo]
125. [ resampled\_data\_size = av\_samples\_get\_buffer\_size(&dst\_linesize, dst\_nb\_channels, ][demo]
126. [ ret, (AVSampleFormat)out\_sample\_fmt, 1); ][demo]
127. [ **if** (resampled\_data\_size <= 0) ][demo]
128. [ \{ ][demo]
129. [ printf("av\_samples\_get\_buffer\_size error \\n"); ][demo]
130. [ **return** \-1; ][demo]
131. [ \} ][demo]
132. [ \} ][demo]
133. [ **else**][demo]
134. [ \{ ][demo]
135. [ printf("swr\_ctx null error \\n"); ][demo]
136. [ **return** \-1; ][demo]
137. [ \} ][demo]
138. [ ][demo]
139. [ //将值返回去][demo]
140. [ memcpy(out\_buf,dst\_data\[0\],resampled\_data\_size); ][demo]
141. [ ][demo]
142. [ **if** (dst\_data) ][demo]
143. [ \{ ][demo]
144. [ av\_freep(&dst\_data\[0\]); ][demo]
145. [ \} ][demo]
146. [ av\_freep(&dst\_data); ][demo]
147. [ dst\_data = NULL; ][demo]
148. [ ][demo]
149. [ **if** (swr\_ctx) ][demo]
150. [ \{ ][demo]
151. [ swr\_free(&swr\_ctx); ][demo]
152. [ \} ][demo]
153. [ **return** resampled\_data\_size; ][demo]
154. [\} ][demo]

[![save_snippets.png][]][demo]

[demo]: /images/20220711/144d8d8bab26423e8e8aee799aae5f4a.png
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[save_snippets.png]: /images/20220711/57b2ed0145b74b09935aaf06c49da497.png