* sometimes desirable to use multiple frames-per-packet to reduce the
* amount of container overhead. This can be done by setting the
* 'frames_per_packet' option to a value 1 to 8.
+ *
+ *
+ * Optional features
+ * Speex encoder supports several optional features, which can be useful
+ * for some conditions.
+ *
+ * Voice Activity Detection
+ * When enabled, voice activity detection detects whether the audio
+ * being encoded is speech or silence/background noise. VAD is always
+ * implicitly activated when encoding in VBR, so the option is only useful
+ * in non-VBR operation. In this case, Speex detects non-speech periods and
+ * encodes them with just enough bits to reproduce the background noise.
+ *
+ * Discontinuous Transmission (DTX)
+ * DTX is an addition to VAD/VBR operation, that allows to stop transmitting
+ * completely when the background noise is stationary.
+ * In file-based operation only 5 bits are used for such frames.
*/
#include <speex/speex.h>
#include <speex/speex_stereo.h>
#include "libavutil/audioconvert.h"
+#include "libavutil/common.h"
#include "libavutil/opt.h"
#include "avcodec.h"
#include "internal.h"
#include "audio_frame_queue.h"
+/* TODO: Think about converting abr, vad, dtx and such flags to a bit field */
typedef struct {
AVClass *class; ///< AVClass for private options
SpeexBits bits; ///< libspeex bitwriter context
float vbr_quality; ///< VBR quality 0.0 to 10.0
int cbr_quality; ///< CBR quality 0 to 10
int abr; ///< flag to enable ABR
+ int vad; ///< flag to enable VAD
+ int dtx; ///< flag to enable DTX
int pkt_frame_count; ///< frame count for the current packet
AudioFrameQueue afq; ///< frame queue
} LibSpeexEncContext;
s->frames_per_packet);
av_log(avctx, AV_LOG_DEBUG, "packet size: %d\n",
avctx->frame_size * s->frames_per_packet);
+ av_log(avctx, AV_LOG_DEBUG, "voice activity detection: %d\n", s->vad);
+ av_log(avctx, AV_LOG_DEBUG, "discontinuous transmission: %d\n", s->dtx);
}
static av_cold int encode_init(AVCodecContext *avctx)
if (avctx->flags & CODEC_FLAG_QSCALE) {
/* VBR */
s->header.vbr = 1;
+ s->vad = 1; /* VAD is always implicitly activated for VBR */
speex_encoder_ctl(s->enc_state, SPEEX_SET_VBR, &s->header.vbr);
s->vbr_quality = av_clipf(avctx->global_quality / (float)FF_QP2LAMBDA,
0.0f, 10.0f);
avctx->bit_rate = s->header.bitrate + (avctx->channels == 2 ? 800 : 0);
}
+ /* VAD is activated with VBR or can be turned on by itself */
+ if (s->vad)
+ speex_encoder_ctl(s->enc_state, SPEEX_SET_VAD, &s->vad);
+
+ /* Activiting Discontinuous Transmission */
+ if (s->dtx) {
+ speex_encoder_ctl(s->enc_state, SPEEX_SET_DTX, &s->dtx);
+ if ( !(s->abr || s->vad || s->header.vbr))
+ av_log(avctx, AV_LOG_WARNING, "DTX is not much of use without ABR, VAD or VBR\n");
+ }
+
/* set encoding complexity */
if (avctx->compression_level > FF_COMPRESSION_DEFAULT) {
complexity = av_clip(avctx->compression_level, 0, 10);
#define OFFSET(x) offsetof(LibSpeexEncContext, x)
#define AE AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
- { "abr", "Use average bit rate", OFFSET(abr), AV_OPT_TYPE_INT, { 0 }, 0, 1, AE },
- { "cbr_quality", "Set quality value (0 to 10) for CBR", OFFSET(cbr_quality), AV_OPT_TYPE_INT, { 8 }, 0, 10, AE },
- { "frames_per_packet", "Number of frames to encode in each packet", OFFSET(frames_per_packet), AV_OPT_TYPE_INT, { 1 }, 1, 8, AE },
+ { "abr", "Use average bit rate", OFFSET(abr), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
+ { "cbr_quality", "Set quality value (0 to 10) for CBR", OFFSET(cbr_quality), AV_OPT_TYPE_INT, { .i64 = 8 }, 0, 10, AE },
+ { "frames_per_packet", "Number of frames to encode in each packet", OFFSET(frames_per_packet), AV_OPT_TYPE_INT, { .i64 = 1 }, 1, 8, AE },
+ { "vad", "Voice Activity Detection", OFFSET(vad), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
+ { "dtx", "Discontinuous Transmission", OFFSET(dtx), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AE },
{ NULL },
};