Beispiel #1
0
// Modify out_layout and return the new value. The intention is reducing the
// loss libswresample's rematrixing will cause by exchanging similar, but
// strictly speaking incompatible channel pairs. For example, 7.1 should be
// changed to 7.1(wide) without dropping the SL/SR channels. (We still leave
// it to libswresample to create the remix matrix.)
static uint64_t fudge_layout_conversion(struct af_instance *af,
                                        uint64_t in, uint64_t out)
{
    for (int n = 0; n < MP_ARRAY_SIZE(fudge_pairs); n++) {
        uint64_t a = mp_chmap_to_lavc(&fudge_pairs[n][0]);
        uint64_t b = mp_chmap_to_lavc(&fudge_pairs[n][1]);
        if ((in & a) == a && (in & b) == 0 &&
            (out & a) == 0 && (out & b) == b)
        {
            out = (out & ~b) | a;

            MP_VERBOSE(af, "Fudge: %s -> %s\n",
                       mp_chmap_to_str(&fudge_pairs[n][0]),
                       mp_chmap_to_str(&fudge_pairs[n][1]));
        }
    }
    return out;
}
Beispiel #2
0
AVCodecParameters *mp_codec_params_to_av(struct mp_codec_params *c)
{
    AVCodecParameters *avp = avcodec_parameters_alloc();
    if (!avp)
        return NULL;

    // If we have lavf demuxer params, they overwrite by definition any others.
    if (c->lav_codecpar) {
        if (avcodec_parameters_copy(avp, c->lav_codecpar) < 0)
            goto error;
        return avp;
    }

    avp->codec_type = mp_to_av_stream_type(c->type);
    avp->codec_id = mp_codec_to_av_codec_id(c->codec);
    avp->codec_tag = c->codec_tag;
    if (c->extradata_size) {
        avp->extradata =
            av_mallocz(c->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
        if (!avp->extradata)
            goto error;
        avp->extradata_size = c->extradata_size;
        memcpy(avp->extradata, c->extradata, avp->extradata_size);
    }
    avp->bits_per_coded_sample = c->bits_per_coded_sample;

    // Video only
    avp->width = c->disp_w;
    avp->height = c->disp_h;

    // Audio only
    avp->sample_rate = c->samplerate;
    avp->bit_rate = c->bitrate;
    avp->block_align = c->block_align;
    avp->channels = c->channels.num;
    if (!mp_chmap_is_unknown(&c->channels))
        avp->channel_layout = mp_chmap_to_lavc(&c->channels);

    return avp;
error:
    avcodec_parameters_free(&avp);
    return NULL;
}
Beispiel #3
0
// Initialization and runtime control
static int control(struct af_instance *af, int cmd, void *arg)
{
    af_ac3enc_t *s  = af->priv;
    static const int default_bit_rate[AC3_MAX_CHANNELS+1] = \
        {0, 96000, 192000, 256000, 384000, 448000, 448000};

    switch (cmd){
    case AF_CONTROL_REINIT: {
        struct mp_audio *in = arg;
        struct mp_audio orig_in = *in;

        if (AF_FORMAT_IS_SPECIAL(in->format) || in->nch < s->cfg_min_channel_num)
            return AF_DETACH;

        mp_audio_set_format(in, s->in_sampleformat);

        if (in->rate != 48000 && in->rate != 44100 && in->rate != 32000)
            in->rate = 48000;
        af->data->rate = in->rate;

        mp_chmap_reorder_to_lavc(&in->channels);
        if (in->nch > AC3_MAX_CHANNELS)
            mp_audio_set_num_channels(in, AC3_MAX_CHANNELS);

        mp_audio_set_format(af->data, AF_FORMAT_AC3_BE);
        mp_audio_set_num_channels(af->data, 2);

        if (!mp_audio_config_equals(in, &orig_in))
            return AF_FALSE;

        s->in_samples = AC3_FRAME_SIZE;
        if (s->cfg_add_iec61937_header) {
            s->out_samples = AC3_FRAME_SIZE;
        } else {
            s->out_samples = AC3_MAX_CODED_FRAME_SIZE / af->data->sstride;
        }
        af->mul = s->out_samples / (double)s->in_samples;

        mp_audio_buffer_reinit(s->pending, in);

        MP_DBG(af, "af_lavcac3enc reinit: %d, %d, %f, %d.\n",
               in->nch, in->rate, af->mul, s->in_samples);

        int bit_rate = s->bit_rate ? s->bit_rate : default_bit_rate[in->nch];

        if (s->lavc_actx->channels != in->nch ||
            s->lavc_actx->sample_rate != in->rate ||
            s->lavc_actx->bit_rate != bit_rate)
        {
            avcodec_close(s->lavc_actx);

            // Put sample parameters
            s->lavc_actx->channels = in->nch;
            s->lavc_actx->channel_layout = mp_chmap_to_lavc(&in->channels);
            s->lavc_actx->sample_rate = in->rate;
            s->lavc_actx->bit_rate = bit_rate;

            if (avcodec_open2(s->lavc_actx, s->lavc_acodec, NULL) < 0) {
                MP_ERR(af, "Couldn't open codec %s, br=%d.\n", "ac3", bit_rate);
                return AF_ERROR;
            }
        }
        if (s->lavc_actx->frame_size != AC3_FRAME_SIZE) {
            MP_ERR(af, "lavcac3enc: unexpected ac3 "
                   "encoder frame size %d\n", s->lavc_actx->frame_size);
            return AF_ERROR;
        }
        return AF_OK;
    }
    }
    return AF_UNKNOWN;
}
Beispiel #4
0
// Initialization and runtime control
static int control(struct af_instance *af, int cmd, void *arg)
{
    af_ac3enc_t *s  = af->priv;
    static const int default_bit_rate[AC3_MAX_CHANNELS+1] = \
        {0, 96000, 192000, 256000, 384000, 448000, 448000};

    switch (cmd){
    case AF_CONTROL_REINIT: {
        struct mp_audio *in = arg;
        struct mp_audio orig_in = *in;

        if (!af_fmt_is_pcm(in->format) || in->nch < s->cfg_min_channel_num)
            return AF_DETACH;

        // At least currently, the AC3 encoder doesn't export sample rates.
        in->rate = 48000;
        select_encode_format(s->lavc_actx, in);

        af->data->rate = in->rate;
        mp_audio_set_format(af->data, AF_FORMAT_S_AC3);
        mp_audio_set_num_channels(af->data, 2);

        if (!mp_audio_config_equals(in, &orig_in))
            return AF_FALSE;

        if (s->cfg_add_iec61937_header) {
            s->out_samples = AC3_FRAME_SIZE;
        } else {
            s->out_samples = AC3_MAX_CODED_FRAME_SIZE / af->data->sstride;
        }

        mp_audio_copy_config(s->input, in);

        talloc_free(s->pending);
        s->pending = NULL;

        MP_DBG(af, "reinit: %d, %d, %d.\n", in->nch, in->rate, s->in_samples);

        int bit_rate = s->bit_rate ? s->bit_rate : default_bit_rate[in->nch];

        if (s->lavc_actx->channels != in->nch ||
            s->lavc_actx->sample_rate != in->rate ||
            s->lavc_actx->bit_rate != bit_rate)
        {
            avcodec_close(s->lavc_actx);

            // Put sample parameters
            s->lavc_actx->sample_fmt = af_to_avformat(in->format);
            s->lavc_actx->channels = in->nch;
            s->lavc_actx->channel_layout = mp_chmap_to_lavc(&in->channels);
            s->lavc_actx->sample_rate = in->rate;
            s->lavc_actx->bit_rate = bit_rate;

            if (avcodec_open2(s->lavc_actx, s->lavc_acodec, NULL) < 0) {
                MP_ERR(af, "Couldn't open codec %s, br=%d.\n", "ac3", bit_rate);
                return AF_ERROR;
            }

            if (s->lavc_actx->frame_size < 1) {
                MP_ERR(af, "encoder didn't specify input frame size\n");
                return AF_ERROR;
            }
        }
        s->in_samples = s->lavc_actx->frame_size;
        mp_audio_realloc(s->input, s->in_samples);
        s->input->samples = 0;
        s->encoder_buffered = 0;
        return AF_OK;
    }
    case AF_CONTROL_RESET:
        if (avcodec_is_open(s->lavc_actx))
            avcodec_flush_buffers(s->lavc_actx);
        talloc_free(s->pending);
        s->pending = NULL;
        s->input->samples = 0;
        s->encoder_buffered = 0;
        return AF_OK;
    }
    return AF_UNKNOWN;
}
Beispiel #5
0
// Attempt to initialize all pads. Return true if all are initialized, or
// false if more data is needed (or on error).
static bool init_pads(struct lavfi *c)
{
    if (!c->graph)
        goto error;

    for (int n = 0; n < c->num_out_pads; n++) {
        struct lavfi_pad *pad = c->out_pads[n];
        if (pad->buffer)
            continue;

        const AVFilter *dst_filter = NULL;
        if (pad->type == MP_FRAME_AUDIO) {
            dst_filter = avfilter_get_by_name("abuffersink");
        } else if (pad->type == MP_FRAME_VIDEO) {
            dst_filter = avfilter_get_by_name("buffersink");
        } else {
            assert(0);
        }

        if (!dst_filter)
            goto error;

        char name[256];
        snprintf(name, sizeof(name), "mpv_sink_%s", pad->name);

        if (avfilter_graph_create_filter(&pad->buffer, dst_filter,
                                         name, NULL, NULL, c->graph) < 0)
            goto error;

        if (avfilter_link(pad->filter, pad->filter_pad, pad->buffer, 0) < 0)
            goto error;
    }

    for (int n = 0; n < c->num_in_pads; n++) {
        struct lavfi_pad *pad = c->in_pads[n];
        if (pad->buffer)
            continue;

        mp_frame_unref(&pad->in_fmt);

        read_pad_input(c, pad);
        // no input data, format unknown, can't init, wait longer.
        if (!pad->pending.type)
            return false;

        if (mp_frame_is_data(pad->pending)) {
            assert(pad->pending.type == pad->type);

            pad->in_fmt = mp_frame_ref(pad->pending);
            if (!pad->in_fmt.type)
                goto error;

            if (pad->in_fmt.type == MP_FRAME_VIDEO)
                mp_image_unref_data(pad->in_fmt.data);
            if (pad->in_fmt.type == MP_FRAME_AUDIO)
                mp_aframe_unref_data(pad->in_fmt.data);
        }

        if (pad->pending.type == MP_FRAME_EOF && !pad->in_fmt.type) {
            // libavfilter makes this painful. Init it with a dummy config,
            // just so we can tell it the stream is EOF.
            if (pad->type == MP_FRAME_AUDIO) {
                struct mp_aframe *fmt = mp_aframe_create();
                mp_aframe_set_format(fmt, AF_FORMAT_FLOAT);
                mp_aframe_set_chmap(fmt, &(struct mp_chmap)MP_CHMAP_INIT_STEREO);
                mp_aframe_set_rate(fmt, 48000);
                pad->in_fmt = (struct mp_frame){MP_FRAME_AUDIO, fmt};
            }
            if (pad->type == MP_FRAME_VIDEO) {
                struct mp_image *fmt = talloc_zero(NULL, struct mp_image);
                mp_image_setfmt(fmt, IMGFMT_420P);
                mp_image_set_size(fmt, 64, 64);
                pad->in_fmt = (struct mp_frame){MP_FRAME_VIDEO, fmt};
            }
        }

        if (pad->in_fmt.type != pad->type)
            goto error;

        AVBufferSrcParameters *params = av_buffersrc_parameters_alloc();
        if (!params)
            goto error;

        pad->timebase = AV_TIME_BASE_Q;

        char *filter_name = NULL;
        if (pad->type == MP_FRAME_AUDIO) {
            struct mp_aframe *fmt = pad->in_fmt.data;
            params->format = af_to_avformat(mp_aframe_get_format(fmt));
            params->sample_rate = mp_aframe_get_rate(fmt);
            struct mp_chmap chmap = {0};
            mp_aframe_get_chmap(fmt, &chmap);
            params->channel_layout = mp_chmap_to_lavc(&chmap);
            pad->timebase = (AVRational){1, mp_aframe_get_rate(fmt)};
            filter_name = "abuffer";
        } else if (pad->type == MP_FRAME_VIDEO) {
            struct mp_image *fmt = pad->in_fmt.data;
            params->format = imgfmt2pixfmt(fmt->imgfmt);
            params->width = fmt->w;
            params->height = fmt->h;
            params->sample_aspect_ratio.num = fmt->params.p_w;
            params->sample_aspect_ratio.den = fmt->params.p_h;
            params->hw_frames_ctx = fmt->hwctx;
            params->frame_rate = av_d2q(fmt->nominal_fps, 1000000);
            filter_name = "buffer";
        } else {
            assert(0);
        }

        params->time_base = pad->timebase;

        const AVFilter *filter = avfilter_get_by_name(filter_name);
        if (filter) {
            char name[256];
            snprintf(name, sizeof(name), "mpv_src_%s", pad->name);

            pad->buffer = avfilter_graph_alloc_filter(c->graph, filter, name);
        }
        if (!pad->buffer) {
            av_free(params);
            goto error;
        }

        int ret = av_buffersrc_parameters_set(pad->buffer, params);
        av_free(params);
        if (ret < 0)
            goto error;

        if (avfilter_init_str(pad->buffer, NULL) < 0)
            goto error;

        if (avfilter_link(pad->buffer, 0, pad->filter, pad->filter_pad) < 0)
            goto error;
    }

    return true;
error:
    MP_FATAL(c, "could not initialize filter pads\n");
    c->failed = true;
    mp_filter_internal_mark_failed(c->f);
    return false;
}
Beispiel #6
0
static bool recreate_graph(struct af_instance *af, struct mp_audio *config)
{
    void *tmp = talloc_new(NULL);
    struct priv *p = af->priv;
    AVFilterContext *in = NULL, *out = NULL, *f_format = NULL;

    if (bstr0(p->cfg_graph).len == 0) {
        MP_FATAL(af, "lavfi: no filter graph set\n");
        return false;
    }

    destroy_graph(af);
    MP_VERBOSE(af, "lavfi: create graph: '%s'\n", p->cfg_graph);

    AVFilterGraph *graph = avfilter_graph_alloc();
    if (!graph)
        goto error;

    if (mp_set_avopts(af->log, graph, p->cfg_avopts) < 0)
        goto error;

    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    if (!outputs || !inputs)
        goto error;

    // Build list of acceptable output sample formats. libavfilter will insert
    // conversion filters if needed.
    static const enum AVSampleFormat sample_fmts[] = {
        AV_SAMPLE_FMT_U8, AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S32,
        AV_SAMPLE_FMT_FLT, AV_SAMPLE_FMT_DBL,
        AV_SAMPLE_FMT_U8P, AV_SAMPLE_FMT_S16P, AV_SAMPLE_FMT_S32P,
        AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_DBLP,
        AV_SAMPLE_FMT_NONE
    };
    char *fmtstr = talloc_strdup(tmp, "");
    for (int n = 0; sample_fmts[n] != AV_SAMPLE_FMT_NONE; n++) {
        const char *name = av_get_sample_fmt_name(sample_fmts[n]);
        if (name) {
            const char *s = fmtstr[0] ? "|" : "";
            fmtstr = talloc_asprintf_append_buffer(fmtstr, "%s%s", s, name);
        }
    }

    char *src_args = talloc_asprintf(tmp,
        "sample_rate=%d:sample_fmt=%s:time_base=%d/%d:"
        "channel_layout=0x%"PRIx64,  config->rate,
        av_get_sample_fmt_name(af_to_avformat(config->format)),
        1, config->rate, mp_chmap_to_lavc(&config->channels));

    if (avfilter_graph_create_filter(&in, avfilter_get_by_name("abuffer"),
                                     "src", src_args, NULL, graph) < 0)
        goto error;

    if (avfilter_graph_create_filter(&out, avfilter_get_by_name("abuffersink"),
                                     "out", NULL, NULL, graph) < 0)
        goto error;

    if (avfilter_graph_create_filter(&f_format, avfilter_get_by_name("aformat"),
                                     "format", fmtstr, NULL, graph) < 0)
        goto error;

    if (avfilter_link(f_format, 0, out, 0) < 0)
        goto error;

    outputs->name = av_strdup("in");
    outputs->filter_ctx = in;

    inputs->name = av_strdup("out");
    inputs->filter_ctx = f_format;

    if (graph_parse(graph, p->cfg_graph, inputs, outputs, NULL) < 0)
        goto error;

    if (avfilter_graph_config(graph, NULL) < 0)
        goto error;

    p->in = in;
    p->out = out;
    p->graph = graph;

    assert(out->nb_inputs == 1);
    assert(in->nb_outputs == 1);

    talloc_free(tmp);
    return true;

error:
    MP_FATAL(af, "Can't configure libavfilter graph.\n");
    avfilter_graph_free(&graph);
    talloc_free(tmp);
    return false;
}
Beispiel #7
0
static bool recreate_graph(struct af_instance *af, struct mp_audio *config)
{
    void *tmp = talloc_new(NULL);
    struct priv *p = af->priv;
    AVFilterContext *in = NULL, *out = NULL;
    int r;

    if (bstr0(p->cfg_graph).len == 0) {
        mp_msg(MSGT_AFILTER, MSGL_FATAL, "lavfi: no filter graph set\n");
        return false;
    }

    destroy_graph(af);
    mp_msg(MSGT_AFILTER, MSGL_V, "lavfi: create graph: '%s'\n", p->cfg_graph);

    AVFilterGraph *graph = avfilter_graph_alloc();
    if (!graph)
        goto error;

    if (parse_avopts(graph, p->cfg_avopts) < 0) {
        mp_msg(MSGT_VFILTER, MSGL_FATAL, "lavfi: could not set opts: '%s'\n",
               p->cfg_avopts);
        goto error;
    }

    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    if (!outputs || !inputs)
        goto error;

    char *src_args = talloc_asprintf(tmp,
        "sample_rate=%d:sample_fmt=%s:channels=%d:time_base=%d/%d:"
        "channel_layout=0x%"PRIx64,  config->rate,
        av_get_sample_fmt_name(af_to_avformat(config->format)),
        config->channels.num, 1, config->rate,
        mp_chmap_to_lavc(&config->channels));

    if (avfilter_graph_create_filter(&in, avfilter_get_by_name("abuffer"),
                                     "src", src_args, NULL, graph) < 0)
        goto error;

    if (avfilter_graph_create_filter(&out, avfilter_get_by_name("abuffersink"),
                                     "out", NULL, NULL, graph) < 0)
        goto error;

    static const enum AVSampleFormat sample_fmts[] = {
        AV_SAMPLE_FMT_U8, AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S32,
        AV_SAMPLE_FMT_FLT, AV_SAMPLE_FMT_DBL,
        AV_SAMPLE_FMT_U8P, AV_SAMPLE_FMT_S16P, AV_SAMPLE_FMT_S32P,
        AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_DBLP,
        AV_SAMPLE_FMT_NONE
    };
    r = av_opt_set_int_list(out, "sample_fmts", sample_fmts,
                            AV_SAMPLE_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
    if (r < 0)
        goto error;

    r = av_opt_set_int(out, "all_channel_counts", 1, AV_OPT_SEARCH_CHILDREN);
    if (r < 0)
        goto error;

    outputs->name = av_strdup("in");
    outputs->filter_ctx = in;

    inputs->name = av_strdup("out");
    inputs->filter_ctx = out;

    if (graph_parse(graph, p->cfg_graph, inputs, outputs, NULL) < 0)
        goto error;

    if (avfilter_graph_config(graph, NULL) < 0)
        goto error;

    p->in = in;
    p->out = out;
    p->graph = graph;

    assert(out->nb_inputs == 1);
    assert(in->nb_outputs == 1);

    talloc_free(tmp);
    return true;

error:
    mp_msg(MSGT_AFILTER, MSGL_FATAL, "Can't configure libavfilter graph.\n");
    avfilter_graph_free(&graph);
    talloc_free(tmp);
    return false;
}
Beispiel #8
0
// open & setup audio device
static int init(struct ao *ao)
{
    struct priv *ac = talloc_zero(ao, struct priv);
    AVCodec *codec;

    ao->priv = ac;

    if (!encode_lavc_available(ao->encode_lavc_ctx)) {
        MP_ERR(ao, "the option --o (output file) must be specified\n");
        return -1;
    }

    pthread_mutex_lock(&ao->encode_lavc_ctx->lock);

    if (encode_lavc_alloc_stream(ao->encode_lavc_ctx,
                                 AVMEDIA_TYPE_AUDIO,
                                 &ac->stream, &ac->codec) < 0) {
      MP_ERR(ao, "could not get a new audio stream\n");
      goto fail;
    }

    codec = ao->encode_lavc_ctx->ac;

    int samplerate = af_select_best_samplerate(ao->samplerate,
                                               codec->supported_samplerates);
    if (samplerate > 0)
        ao->samplerate = samplerate;

    // TODO: Remove this redundancy with encode_lavc_alloc_stream also
    // setting the time base.
    // Using codec->time_bvase is deprecated, but needed for older lavf.
    ac->stream->time_base.num = 1;
    ac->stream->time_base.den = ao->samplerate;
    ac->codec->time_base.num = 1;
    ac->codec->time_base.den = ao->samplerate;

    ac->codec->sample_rate = ao->samplerate;

    struct mp_chmap_sel sel = {0};
    mp_chmap_sel_add_any(&sel);
    if (!ao_chmap_sel_adjust2(ao, &sel, &ao->channels, false))
        goto fail;
    mp_chmap_reorder_to_lavc(&ao->channels);
    ac->codec->channels = ao->channels.num;
    ac->codec->channel_layout = mp_chmap_to_lavc(&ao->channels);

    ac->codec->sample_fmt = AV_SAMPLE_FMT_NONE;

    select_format(ao, codec);

    ac->sample_size = af_fmt_to_bytes(ao->format);
    ac->codec->sample_fmt = af_to_avformat(ao->format);
    ac->codec->bits_per_raw_sample = ac->sample_size * 8;

    if (encode_lavc_open_codec(ao->encode_lavc_ctx, ac->codec) < 0)
        goto fail;

    ac->pcmhack = 0;
    if (ac->codec->frame_size <= 1)
        ac->pcmhack = av_get_bits_per_sample(ac->codec->codec_id) / 8;

    if (ac->pcmhack)
        ac->aframesize = 16384; // "enough"
    else
        ac->aframesize = ac->codec->frame_size;

    // enough frames for at least 0.25 seconds
    ac->framecount = ceil(ao->samplerate * 0.25 / ac->aframesize);
    // but at least one!
    ac->framecount = FFMAX(ac->framecount, 1);

    ac->savepts = AV_NOPTS_VALUE;
    ac->lastpts = AV_NOPTS_VALUE;

    ao->untimed = true;

    if (ao->channels.num > AV_NUM_DATA_POINTERS)
        goto fail;

    pthread_mutex_unlock(&ao->encode_lavc_ctx->lock);
    return 0;

fail:
    pthread_mutex_unlock(&ao->encode_lavc_ctx->lock);
    ac->shutdown = true;
    return -1;
}
Beispiel #9
0
// open & setup audio device
static int init(struct ao *ao)
{
    struct priv *ac = talloc_zero(ao, struct priv);
    AVCodec *codec;

    ao->priv = ac;

    if (!encode_lavc_available(ao->encode_lavc_ctx)) {
        MP_ERR(ao, "the option --o (output file) must be specified\n");
        return -1;
    }

    pthread_mutex_lock(&ao->encode_lavc_ctx->lock);

    ac->stream = encode_lavc_alloc_stream(ao->encode_lavc_ctx,
                                          AVMEDIA_TYPE_AUDIO);

    if (!ac->stream) {
        MP_ERR(ao, "could not get a new audio stream\n");
        goto fail;
    }

    codec = encode_lavc_get_codec(ao->encode_lavc_ctx, ac->stream);

    // ac->stream->time_base.num = 1;
    // ac->stream->time_base.den = ao->samplerate;
    // doing this breaks mpeg2ts in ffmpeg
    // which doesn't properly force the time base to be 90000
    // furthermore, ffmpeg.c doesn't do this either and works

    ac->stream->codec->time_base.num = 1;
    ac->stream->codec->time_base.den = ao->samplerate;

    ac->stream->codec->sample_rate = ao->samplerate;

    struct mp_chmap_sel sel = {0};
    mp_chmap_sel_add_any(&sel);
    if (!ao_chmap_sel_adjust(ao, &sel, &ao->channels))
        goto fail;
    mp_chmap_reorder_to_lavc(&ao->channels);
    ac->stream->codec->channels = ao->channels.num;
    ac->stream->codec->channel_layout = mp_chmap_to_lavc(&ao->channels);

    ac->stream->codec->sample_fmt = AV_SAMPLE_FMT_NONE;

    select_format(ao, codec);

    ac->sample_size = af_fmt2bits(ao->format) / 8;
    ac->stream->codec->sample_fmt = af_to_avformat(ao->format);
    ac->stream->codec->bits_per_raw_sample = ac->sample_size * 8;

    if (encode_lavc_open_codec(ao->encode_lavc_ctx, ac->stream) < 0)
        goto fail;

    ac->pcmhack = 0;
    if (ac->stream->codec->frame_size <= 1)
        ac->pcmhack = av_get_bits_per_sample(ac->stream->codec->codec_id) / 8;

    if (ac->pcmhack) {
        ac->aframesize = 16384; // "enough"
        ac->buffer_size =
            ac->aframesize * ac->pcmhack * ao->channels.num * 2 + 200;
    } else {
        ac->aframesize = ac->stream->codec->frame_size;
        ac->buffer_size =
            ac->aframesize * ac->sample_size * ao->channels.num * 2 + 200;
    }
    if (ac->buffer_size < FF_MIN_BUFFER_SIZE)
        ac->buffer_size = FF_MIN_BUFFER_SIZE;
    ac->buffer = talloc_size(ac, ac->buffer_size);

    // enough frames for at least 0.25 seconds
    ac->framecount = ceil(ao->samplerate * 0.25 / ac->aframesize);
    // but at least one!
    ac->framecount = FFMAX(ac->framecount, 1);

    ac->savepts = MP_NOPTS_VALUE;
    ac->lastpts = MP_NOPTS_VALUE;

    ao->untimed = true;

    pthread_mutex_unlock(&ao->encode_lavc_ctx->lock);
    return 0;

fail:
    pthread_mutex_unlock(&ao->encode_lavc_ctx->lock);
    return -1;
}