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48 #include <alsa/asoundlib.h>
90 s->period_size, 1.5E-6);
106 snd_pcm_sframes_t delay = 0;
116 while ((res = snd_pcm_readi(
s->h,
s->pkt->data +
s->pkt->size,
s->period_size -
s->pkt->size /
s->frame_size)) < 0) {
117 if (res == -EAGAIN) {
128 s->pkt->size += res *
s->frame_size;
129 }
while (
s->pkt->size <
s->period_size *
s->frame_size);
133 snd_pcm_delay(
s->h, &delay);
134 dts -=
av_rescale(delay + res, 1000000,
s->sample_rate);
136 s->last_period = res;
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
enum AVMediaType codec_type
General type of the encoded data.
AVStream * avformat_new_stream(AVFormatContext *s, const struct AVCodec *c)
Add a new stream to a media file.
int nb_channels
Number of channels in this layout.
const AVInputFormat ff_alsa_demuxer
static av_cold int read_close(AVFormatContext *ctx)
TimeFilter * ff_timefilter_new(double time_base, double period, double bandwidth)
Create a new Delay Locked Loop time filter.
@ AV_CLASS_CATEGORY_DEVICE_AUDIO_INPUT
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
int frame_size
Audio only.
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
av_cold int ff_alsa_open(AVFormatContext *ctx, snd_pcm_stream_t mode, unsigned int *sample_rate, int channels, enum AVCodecID *codec_id)
Open an ALSA PCM.
AVCodecParameters * codecpar
Codec parameters associated with this stream.
#define LIBAVUTIL_VERSION_INT
static int read_header(FFV1Context *f)
Describe the class of an AVClass context structure.
static const AVClass alsa_demuxer_class
static av_cold int audio_read_header(AVFormatContext *s1)
const char * av_default_item_name(void *ptr)
Return the context name.
AVChannelLayout ch_layout
Audio only.
void av_packet_move_ref(AVPacket *dst, AVPacket *src)
Move every field in src to dst and reset src.
av_cold int ff_alsa_close(AVFormatContext *s1)
Close the ALSA PCM.
int sample_rate
Audio only.
AVCodecID
Identify the syntax and semantics of the bitstream.
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
void ff_timefilter_reset(TimeFilter *self)
Reset the filter.
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
double ff_timefilter_update(TimeFilter *self, double system_time, double period)
Update the filter.
int64_t av_rescale(int64_t a, int64_t b, int64_t c)
Rescale a 64-bit integer with rounding to nearest.
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
static int audio_get_device_list(AVFormatContext *h, AVDeviceInfoList *device_list)
int ff_alsa_xrun_recover(AVFormatContext *s1, int err)
Try to recover from ALSA buffer underrun.
int64_t av_gettime(void)
Get the current time in microseconds.
static const AVOption options[]
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
This structure stores compressed data.
int ff_alsa_get_device_list(AVDeviceInfoList *device_list, snd_pcm_stream_t stream_type)
#define flags(name, subs,...)
static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)