FFmpeg
af_amerge.c
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2011 Nicolas George <nicolas.george@normalesup.org>
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
14  * GNU 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  * @file
23  * Audio merging filter
24  */
25 
26 #include "libavutil/avstring.h"
27 #include "libavutil/bprint.h"
29 #include "libavutil/opt.h"
30 #include "avfilter.h"
31 #include "filters.h"
32 #include "audio.h"
33 #include "internal.h"
34 
35 #define SWR_CH_MAX 64
36 
37 typedef struct AMergeContext {
38  const AVClass *class;
39  int nb_inputs;
40  int route[SWR_CH_MAX]; /**< channels routing, see copy_samples */
41  int bps;
42  struct amerge_input {
43  int nb_ch; /**< number of channels for the input */
44  } *in;
46 
47 #define OFFSET(x) offsetof(AMergeContext, x)
48 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
49 
50 static const AVOption amerge_options[] = {
51  { "inputs", "specify the number of inputs", OFFSET(nb_inputs),
52  AV_OPT_TYPE_INT, { .i64 = 2 }, 1, SWR_CH_MAX, FLAGS },
53  { NULL }
54 };
55 
56 AVFILTER_DEFINE_CLASS(amerge);
57 
59 {
60  AMergeContext *s = ctx->priv;
61 
62  av_freep(&s->in);
63 }
64 
66 {
67  static const enum AVSampleFormat packed_sample_fmts[] = {
74  };
75  AMergeContext *s = ctx->priv;
76  int64_t inlayout[SWR_CH_MAX], outlayout = 0;
78  int i, ret, overlap = 0, nb_ch = 0;
79 
80  for (i = 0; i < s->nb_inputs; i++) {
81  if (!ctx->inputs[i]->incfg.channel_layouts ||
82  !ctx->inputs[i]->incfg.channel_layouts->nb_channel_layouts) {
84  "No channel layout for input %d\n", i + 1);
85  return AVERROR(EAGAIN);
86  }
87  inlayout[i] = ctx->inputs[i]->incfg.channel_layouts->channel_layouts[0];
88  if (ctx->inputs[i]->incfg.channel_layouts->nb_channel_layouts > 1) {
89  char buf[256];
90  av_get_channel_layout_string(buf, sizeof(buf), 0, inlayout[i]);
91  av_log(ctx, AV_LOG_INFO, "Using \"%s\" for input %d\n", buf, i + 1);
92  }
93  s->in[i].nb_ch = FF_LAYOUT2COUNT(inlayout[i]);
94  if (s->in[i].nb_ch) {
95  overlap++;
96  } else {
97  s->in[i].nb_ch = av_get_channel_layout_nb_channels(inlayout[i]);
98  if (outlayout & inlayout[i])
99  overlap++;
100  outlayout |= inlayout[i];
101  }
102  nb_ch += s->in[i].nb_ch;
103  }
104  if (nb_ch > SWR_CH_MAX) {
105  av_log(ctx, AV_LOG_ERROR, "Too many channels (max %d)\n", SWR_CH_MAX);
106  return AVERROR(EINVAL);
107  }
108  if (overlap) {
110  "Input channel layouts overlap: "
111  "output layout will be determined by the number of distinct input channels\n");
112  for (i = 0; i < nb_ch; i++)
113  s->route[i] = i;
114  outlayout = av_get_default_channel_layout(nb_ch);
115  if (!outlayout && nb_ch)
116  outlayout = 0xFFFFFFFFFFFFFFFFULL >> (64 - nb_ch);
117  } else {
118  int *route[SWR_CH_MAX];
119  int c, out_ch_number = 0;
120 
121  route[0] = s->route;
122  for (i = 1; i < s->nb_inputs; i++)
123  route[i] = route[i - 1] + s->in[i - 1].nb_ch;
124  for (c = 0; c < 64; c++)
125  for (i = 0; i < s->nb_inputs; i++)
126  if ((inlayout[i] >> c) & 1)
127  *(route[i]++) = out_ch_number++;
128  }
129  if ((ret = ff_set_common_formats_from_list(ctx, packed_sample_fmts)) < 0)
130  return ret;
131  for (i = 0; i < s->nb_inputs; i++) {
132  layouts = NULL;
133  if ((ret = ff_add_channel_layout(&layouts, inlayout[i])) < 0)
134  return ret;
135  if ((ret = ff_channel_layouts_ref(layouts, &ctx->inputs[i]->outcfg.channel_layouts)) < 0)
136  return ret;
137  }
138  layouts = NULL;
139  if ((ret = ff_add_channel_layout(&layouts, outlayout)) < 0)
140  return ret;
141  if ((ret = ff_channel_layouts_ref(layouts, &ctx->outputs[0]->incfg.channel_layouts)) < 0)
142  return ret;
143 
145 }
146 
147 static int config_output(AVFilterLink *outlink)
148 {
149  AVFilterContext *ctx = outlink->src;
150  AMergeContext *s = ctx->priv;
151  AVBPrint bp;
152  int i;
153 
154  s->bps = av_get_bytes_per_sample(ctx->outputs[0]->format);
155  outlink->time_base = ctx->inputs[0]->time_base;
156 
158  for (i = 0; i < s->nb_inputs; i++) {
159  av_bprintf(&bp, "%sin%d:", i ? " + " : "", i);
160  av_bprint_channel_layout(&bp, -1, ctx->inputs[i]->channel_layout);
161  }
162  av_bprintf(&bp, " -> out:");
163  av_bprint_channel_layout(&bp, -1, ctx->outputs[0]->channel_layout);
164  av_log(ctx, AV_LOG_VERBOSE, "%s\n", bp.str);
165 
166  return 0;
167 }
168 
169 /**
170  * Copy samples from several input streams to one output stream.
171  * @param nb_inputs number of inputs
172  * @param in inputs; used only for the nb_ch field;
173  * @param route routing values;
174  * input channel i goes to output channel route[i];
175  * i < in[0].nb_ch are the channels from the first output;
176  * i >= in[0].nb_ch are the channels from the second output
177  * @param ins pointer to the samples of each inputs, in packed format;
178  * will be left at the end of the copied samples
179  * @param outs pointer to the samples of the output, in packet format;
180  * must point to a buffer big enough;
181  * will be left at the end of the copied samples
182  * @param ns number of samples to copy
183  * @param bps bytes per sample
184  */
185 static inline void copy_samples(int nb_inputs, struct amerge_input in[],
186  int *route, uint8_t *ins[],
187  uint8_t **outs, int ns, int bps)
188 {
189  int *route_cur;
190  int i, c, nb_ch = 0;
191 
192  for (i = 0; i < nb_inputs; i++)
193  nb_ch += in[i].nb_ch;
194  while (ns--) {
195  route_cur = route;
196  for (i = 0; i < nb_inputs; i++) {
197  for (c = 0; c < in[i].nb_ch; c++) {
198  memcpy((*outs) + bps * *(route_cur++), ins[i], bps);
199  ins[i] += bps;
200  }
201  }
202  *outs += nb_ch * bps;
203  }
204 }
205 
206 static void free_frames(int nb_inputs, AVFrame **input_frames)
207 {
208  int i;
209  for (i = 0; i < nb_inputs; i++)
210  av_frame_free(&input_frames[i]);
211 }
212 
213 static int try_push_frame(AVFilterContext *ctx, int nb_samples)
214 {
215  AMergeContext *s = ctx->priv;
216  AVFilterLink *outlink = ctx->outputs[0];
217  int i, ret;
218  AVFrame *outbuf, *inbuf[SWR_CH_MAX] = { NULL };
219  uint8_t *outs, *ins[SWR_CH_MAX];
220 
221  for (i = 0; i < ctx->nb_inputs; i++) {
222  ret = ff_inlink_consume_samples(ctx->inputs[i], nb_samples, nb_samples, &inbuf[i]);
223  if (ret < 0) {
224  free_frames(i, inbuf);
225  return ret;
226  }
227  ins[i] = inbuf[i]->data[0];
228  }
229 
230  outbuf = ff_get_audio_buffer(ctx->outputs[0], nb_samples);
231  if (!outbuf) {
232  free_frames(s->nb_inputs, inbuf);
233  return AVERROR(ENOMEM);
234  }
235 
236  outs = outbuf->data[0];
237  outbuf->pts = inbuf[0]->pts;
238 
239  outbuf->nb_samples = nb_samples;
240  outbuf->channel_layout = outlink->channel_layout;
241  outbuf->channels = outlink->channels;
242 
243  while (nb_samples) {
244  /* Unroll the most common sample formats: speed +~350% for the loop,
245  +~13% overall (including two common decoders) */
246  switch (s->bps) {
247  case 1:
248  copy_samples(s->nb_inputs, s->in, s->route, ins, &outs, nb_samples, 1);
249  break;
250  case 2:
251  copy_samples(s->nb_inputs, s->in, s->route, ins, &outs, nb_samples, 2);
252  break;
253  case 4:
254  copy_samples(s->nb_inputs, s->in, s->route, ins, &outs, nb_samples, 4);
255  break;
256  default:
257  copy_samples(s->nb_inputs, s->in, s->route, ins, &outs, nb_samples, s->bps);
258  break;
259  }
260 
261  nb_samples = 0;
262  }
263 
264  free_frames(s->nb_inputs, inbuf);
265  return ff_filter_frame(ctx->outputs[0], outbuf);
266 }
267 
269 {
270  int i, status;
271  int ret, nb_samples;
272  int64_t pts;
273 
275 
276  nb_samples = ff_inlink_queued_samples(ctx->inputs[0]);
277  for (i = 1; i < ctx->nb_inputs && nb_samples > 0; i++) {
278  nb_samples = FFMIN(ff_inlink_queued_samples(ctx->inputs[i]), nb_samples);
279  }
280 
281  if (nb_samples) {
282  ret = try_push_frame(ctx, nb_samples);
283  if (ret < 0)
284  return ret;
285  }
286 
287  for (i = 0; i < ctx->nb_inputs; i++) {
288  if (ff_inlink_queued_samples(ctx->inputs[i]))
289  continue;
290 
291  if (ff_inlink_acknowledge_status(ctx->inputs[i], &status, &pts)) {
292  ff_outlink_set_status(ctx->outputs[0], status, pts);
293  return 0;
294  } else if (ff_outlink_frame_wanted(ctx->outputs[0])) {
295  ff_inlink_request_frame(ctx->inputs[i]);
296  return 0;
297  }
298  }
299 
300  return 0;
301 }
302 
304 {
305  AMergeContext *s = ctx->priv;
306  int i, ret;
307 
308  s->in = av_calloc(s->nb_inputs, sizeof(*s->in));
309  if (!s->in)
310  return AVERROR(ENOMEM);
311  for (i = 0; i < s->nb_inputs; i++) {
312  char *name = av_asprintf("in%d", i);
313  AVFilterPad pad = {
314  .name = name,
315  .type = AVMEDIA_TYPE_AUDIO,
316  };
317  if (!name)
318  return AVERROR(ENOMEM);
319  if ((ret = ff_append_inpad_free_name(ctx, &pad)) < 0)
320  return ret;
321  }
322  return 0;
323 }
324 
325 static const AVFilterPad amerge_outputs[] = {
326  {
327  .name = "default",
328  .type = AVMEDIA_TYPE_AUDIO,
329  .config_props = config_output,
330  },
331 };
332 
334  .name = "amerge",
335  .description = NULL_IF_CONFIG_SMALL("Merge two or more audio streams into "
336  "a single multi-channel stream."),
337  .priv_size = sizeof(AMergeContext),
338  .init = init,
339  .uninit = uninit,
340  .activate = activate,
341  .inputs = NULL,
344  .priv_class = &amerge_class,
346 };
ff_get_audio_buffer
AVFrame * ff_get_audio_buffer(AVFilterLink *link, int nb_samples)
Request an audio samples buffer with a specific set of permissions.
Definition: audio.c:88
AVFilterChannelLayouts
A list of supported channel layouts.
Definition: formats.h:85
AV_LOG_WARNING
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:186
AMergeContext::bps
int bps
Definition: af_amerge.c:41
name
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default minimum maximum flags name is the option name
Definition: writing_filters.txt:88
status
they must not be accessed directly The fifo field contains the frames that are queued in the input for processing by the filter The status_in and status_out fields contains the queued status(EOF or error) of the link
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
opt.h
try_push_frame
static int try_push_frame(AVFilterContext *ctx, int nb_samples)
Definition: af_amerge.c:213
av_bprint_init
void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max)
Definition: bprint.c:68
ff_filter_frame
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
Send a frame of data to the next filter.
Definition: avfilter.c:1018
ff_channel_layouts_ref
int ff_channel_layouts_ref(AVFilterChannelLayouts *f, AVFilterChannelLayouts **ref)
Add *ref as a new reference to f.
Definition: formats.c:550
layouts
enum MovChannelLayoutTag * layouts
Definition: mov_chan.c:434
ff_af_amerge
const AVFilter ff_af_amerge
Definition: af_amerge.c:333
av_asprintf
char * av_asprintf(const char *fmt,...)
Definition: avstring.c:113
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:112
amerge_outputs
static const AVFilterPad amerge_outputs[]
Definition: af_amerge.c:325
av_get_channel_layout_string
void av_get_channel_layout_string(char *buf, int buf_size, int nb_channels, uint64_t channel_layout)
Return a description of a channel layout.
Definition: channel_layout.c:217
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:303
AVFrame::pts
int64_t pts
Presentation timestamp in time_base units (time when frame should be shown to user).
Definition: frame.h:396
AMergeContext::route
int route[SWR_CH_MAX]
channels routing, see copy_samples
Definition: af_amerge.c:40
AVOption
AVOption.
Definition: opt.h:247
FILTER_QUERY_FUNC
#define FILTER_QUERY_FUNC(func)
Definition: internal.h:168
AMergeContext::amerge_input
Definition: af_amerge.c:42
AV_LOG_VERBOSE
#define AV_LOG_VERBOSE
Detailed information.
Definition: log.h:196
ff_set_common_all_samplerates
int ff_set_common_all_samplerates(AVFilterContext *ctx)
Equivalent to ff_set_common_samplerates(ctx, ff_all_samplerates())
Definition: formats.c:689
AVFilter::name
const char * name
Filter name.
Definition: avfilter.h:153
AVFrame::data
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:317
FF_LAYOUT2COUNT
#define FF_LAYOUT2COUNT(l)
Decode a channel count encoded as a channel layout.
Definition: formats.h:108
uninit
static av_cold void uninit(AVFilterContext *ctx)
Definition: af_amerge.c:58
FF_FILTER_FORWARD_STATUS_BACK_ALL
#define FF_FILTER_FORWARD_STATUS_BACK_ALL(outlink, filter)
Forward the status on an output link to all input links.
Definition: filters.h:212
init
static av_cold int init(AVFilterContext *ctx)
Definition: af_amerge.c:303
AV_BPRINT_SIZE_AUTOMATIC
#define AV_BPRINT_SIZE_AUTOMATIC
pts
static int64_t pts
Definition: transcode_aac.c:653
AMergeContext
Definition: af_amerge.c:37
AVFILTER_FLAG_DYNAMIC_INPUTS
#define AVFILTER_FLAG_DYNAMIC_INPUTS
The number of the filter inputs is not determined just by AVFilter.inputs.
Definition: avfilter.h:110
AVFilterPad
A filter pad used for either input or output.
Definition: internal.h:50
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
av_cold
#define av_cold
Definition: attributes.h:90
inputs
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several inputs
Definition: filter_design.txt:243
ff_outlink_set_status
static void ff_outlink_set_status(AVFilterLink *link, int status, int64_t pts)
Set the status field of a link from the source filter.
Definition: filters.h:189
ff_add_channel_layout
int ff_add_channel_layout(AVFilterChannelLayouts **l, uint64_t channel_layout)
Definition: formats.c:426
amerge_options
static const AVOption amerge_options[]
Definition: af_amerge.c:50
ff_inlink_request_frame
void ff_inlink_request_frame(AVFilterLink *link)
Mark that a frame is wanted on the link.
Definition: avfilter.c:1534
s
#define s(width, name)
Definition: cbs_vp9.c:257
query_formats
static int query_formats(AVFilterContext *ctx)
Definition: af_amerge.c:65
AVFrame::channels
int channels
number of audio channels, only used for audio.
Definition: frame.h:592
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
av_bprint_channel_layout
void av_bprint_channel_layout(struct AVBPrint *bp, int nb_channels, uint64_t channel_layout)
Append a description of a channel layout to a bprint buffer.
Definition: channel_layout.c:183
ff_set_common_formats_from_list
int ff_set_common_formats_from_list(AVFilterContext *ctx, const int *fmts)
Equivalent to ff_set_common_formats(ctx, ff_make_format_list(fmts))
Definition: formats.c:705
activate
static int activate(AVFilterContext *ctx)
Definition: af_amerge.c:268
filters.h
ctx
AVFormatContext * ctx
Definition: movenc.c:48
AMergeContext::amerge_input::nb_ch
int nb_ch
number of channels for the input
Definition: af_amerge.c:43
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
ff_inlink_consume_samples
int ff_inlink_consume_samples(AVFilterLink *link, unsigned min, unsigned max, AVFrame **rframe)
Take samples from the link's FIFO and update the link's stats.
Definition: avfilter.c:1436
NULL
#define NULL
Definition: coverity.c:32
ff_append_inpad_free_name
int ff_append_inpad_free_name(AVFilterContext *f, AVFilterPad *p)
Definition: avfilter.c:144
AMergeContext::in
struct AMergeContext::amerge_input * in
ff_inlink_acknowledge_status
int ff_inlink_acknowledge_status(AVFilterLink *link, int *rstatus, int64_t *rpts)
Test and acknowledge the change of status on the link.
Definition: avfilter.c:1371
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
av_get_channel_layout_nb_channels
int av_get_channel_layout_nb_channels(uint64_t channel_layout)
Return the number of channels in the channel layout.
Definition: channel_layout.c:226
OFFSET
#define OFFSET(x)
Definition: af_amerge.c:47
for
for(j=16;j >0;--j)
Definition: h264pred_template.c:469
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
bps
unsigned bps
Definition: movenc.c:1596
AV_SAMPLE_FMT_NONE
@ AV_SAMPLE_FMT_NONE
Definition: samplefmt.h:59
AVFrame::channel_layout
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:463
ns
#define ns(max_value, name, subs,...)
Definition: cbs_av1.c:682
AV_LOG_INFO
#define AV_LOG_INFO
Standard information.
Definition: log.h:191
internal.h
AVFrame::nb_samples
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:369
bprint.h
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:271
av_get_bytes_per_sample
int av_get_bytes_per_sample(enum AVSampleFormat sample_fmt)
Return number of bytes per sample.
Definition: samplefmt.c:106
AV_SAMPLE_FMT_U8
@ AV_SAMPLE_FMT_U8
unsigned 8 bits
Definition: samplefmt.h:60
AVFILTER_DEFINE_CLASS
AVFILTER_DEFINE_CLASS(amerge)
FLAGS
#define FLAGS
Definition: af_amerge.c:48
AVSampleFormat
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
AV_SAMPLE_FMT_S16
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition: samplefmt.h:61
AVFilterPad::name
const char * name
Pad name.
Definition: internal.h:56
ff_inlink_queued_samples
int ff_inlink_queued_samples(AVFilterLink *link)
Definition: avfilter.c:1396
av_calloc
void * av_calloc(size_t nmemb, size_t size)
Definition: mem.c:271
copy_samples
static void copy_samples(int nb_inputs, struct amerge_input in[], int *route, uint8_t *ins[], uint8_t **outs, int ns, int bps)
Copy samples from several input streams to one output stream.
Definition: af_amerge.c:185
AVFilter
Filter definition.
Definition: avfilter.h:149
ret
ret
Definition: filter_design.txt:187
free_frames
static void free_frames(int nb_inputs, AVFrame **input_frames)
Definition: af_amerge.c:206
av_bprintf
void av_bprintf(AVBPrint *buf, const char *fmt,...)
Definition: bprint.c:93
SWR_CH_MAX
#define SWR_CH_MAX
Definition: af_amerge.c:35
config_output
static int config_output(AVFilterLink *outlink)
Definition: af_amerge.c:147
channel_layout.h
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:224
avfilter.h
AVFilterContext
An instance of a filter.
Definition: avfilter.h:386
audio.h
av_get_default_channel_layout
int64_t av_get_default_channel_layout(int nb_channels)
Return default channel layout for a given number of channels.
Definition: channel_layout.c:231
FILTER_OUTPUTS
#define FILTER_OUTPUTS(array)
Definition: internal.h:192
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:35
AMergeContext::nb_inputs
int nb_inputs
Definition: af_amerge.c:39
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
ff_outlink_frame_wanted
the definition of that something depends on the semantic of the filter The callback must examine the status of the filter s links and proceed accordingly The status of output links is stored in the status_in and status_out fields and tested by the ff_outlink_frame_wanted() function. If this function returns true
AV_SAMPLE_FMT_DBL
@ AV_SAMPLE_FMT_DBL
double
Definition: samplefmt.h:64
avstring.h
AV_SAMPLE_FMT_S32
@ AV_SAMPLE_FMT_S32
signed 32 bits
Definition: samplefmt.h:62
AV_SAMPLE_FMT_FLT
@ AV_SAMPLE_FMT_FLT
float
Definition: samplefmt.h:63