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af_apad.c
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1 /*
2  * Copyright (c) 2012 Michael Niedermayer
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  *
20  */
21 
22 /**
23  * @file
24  * audio pad filter.
25  *
26  * Based on af_aresample.c
27  */
28 
29 #include "libavutil/avstring.h"
31 #include "libavutil/opt.h"
32 #include "libavutil/samplefmt.h"
33 #include "libavutil/avassert.h"
34 #include "avfilter.h"
35 #include "audio.h"
36 #include "internal.h"
37 
38 typedef struct {
39  const AVClass *class;
40  int64_t next_pts;
41 
43  int64_t pad_len;
44  int64_t whole_len;
45 } APadContext;
46 
47 #define OFFSET(x) offsetof(APadContext, x)
48 #define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
49 
50 static const AVOption apad_options[] = {
51  { "packet_size", "set silence packet size", OFFSET(packet_size), AV_OPT_TYPE_INT, { .i64 = 4096 }, 0, INT_MAX, A },
52  { "pad_len", "number of samples of silence to add", OFFSET(pad_len), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, A },
53  { "whole_len", "target number of samples in the audio stream", OFFSET(whole_len), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, A },
54  { NULL },
55 };
56 
58 
59 static av_cold int init(AVFilterContext *ctx, const char *args)
60 {
61  int ret;
62  APadContext *apad = ctx->priv;
63 
64  apad->class = &apad_class;
65  apad->next_pts = AV_NOPTS_VALUE;
66 
67  av_opt_set_defaults(apad);
68 
69  if ((ret = av_opt_set_from_string(apad, args, NULL, "=", ":")) < 0)
70  return ret;
71 
72  if (apad->whole_len && apad->pad_len) {
73  av_log(ctx, AV_LOG_ERROR, "Both whole and pad length are set, this is not possible\n");
74  return AVERROR(EINVAL);
75  }
76 
77  return 0;
78 }
79 
81 {
82  AVFilterContext *ctx = inlink->dst;
83  APadContext *apad = ctx->priv;
84 
85  if (apad->whole_len)
86  apad->whole_len -= frame->audio->nb_samples;
87 
88  apad->next_pts = frame->pts + av_rescale_q(frame->audio->nb_samples, (AVRational){1, inlink->sample_rate}, inlink->time_base);
89  return ff_filter_frame(ctx->outputs[0], frame);
90 }
91 
92 static int request_frame(AVFilterLink *outlink)
93 {
94  AVFilterContext *ctx = outlink->src;
95  APadContext *apad = ctx->priv;
96  int ret;
97 
98  ret = ff_request_frame(ctx->inputs[0]);
99 
100  if (ret == AVERROR_EOF) {
101  int n_out = apad->packet_size;
102  AVFilterBufferRef *outsamplesref;
103 
104  if (apad->whole_len > 0) {
105  apad->pad_len = apad->whole_len;
106  apad->whole_len = 0;
107  }
108  if (apad->pad_len > 0) {
109  n_out = FFMIN(n_out, apad->pad_len);
110  apad->pad_len -= n_out;
111  }
112 
113  if(!n_out)
114  return AVERROR_EOF;
115 
116  outsamplesref = ff_get_audio_buffer(outlink, AV_PERM_WRITE, n_out);
117  if (!outsamplesref)
118  return AVERROR(ENOMEM);
119 
120  av_assert0(outsamplesref->audio->sample_rate == outlink->sample_rate);
121  av_assert0(outsamplesref->audio->nb_samples == n_out);
122 
123  av_samples_set_silence(outsamplesref->extended_data, 0,
124  n_out,
125  outsamplesref->audio->channels,
126  outsamplesref->format);
127 
128  outsamplesref->pts = apad->next_pts;
129  if (apad->next_pts != AV_NOPTS_VALUE)
130  apad->next_pts += av_rescale_q(n_out, (AVRational){1, outlink->sample_rate}, outlink->time_base);
131 
132  return ff_filter_frame(outlink, outsamplesref);
133  }
134  return ret;
135 }
136 
137 static const AVFilterPad apad_inputs[] = {
138  {
139  .name = "default",
140  .type = AVMEDIA_TYPE_AUDIO,
141  .filter_frame = filter_frame,
142  .min_perms = AV_PERM_READ,
143  },
144  { NULL },
145 };
146 
147 static const AVFilterPad apad_outputs[] = {
148  {
149  .name = "default",
150  .request_frame = request_frame,
151  .type = AVMEDIA_TYPE_AUDIO,
152  },
153  { NULL },
154 };
155 
157  .name = "apad",
158  .description = NULL_IF_CONFIG_SMALL("Pad audio with silence."),
159  .init = init,
160  .priv_size = sizeof(APadContext),
161  .inputs = apad_inputs,
162  .outputs = apad_outputs,
163  .priv_class = &apad_class,
164 };