[FFmpeg-devel] [PATCH 1/2] lavfi: add astreamsync audio filter.
Stefano Sabatini
stefasab at gmail.com
Sat Dec 24 13:32:45 CET 2011
On date Friday 2011-12-23 14:17:13 +0100, Nicolas George encoded:
>
> Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
> ---
> Changelog | 1 +
> doc/filters.texi | 29 ++++++
> libavfilter/Makefile | 1 +
> libavfilter/af_astreamsync.c | 204 ++++++++++++++++++++++++++++++++++++++++++
> libavfilter/allfilters.c | 1 +
> 5 files changed, 236 insertions(+), 0 deletions(-)
> create mode 100644 libavfilter/af_astreamsync.c
[...]
> diff --git a/libavfilter/af_astreamsync.c b/libavfilter/af_astreamsync.c
> new file mode 100644
> index 0000000..66a8b63
> --- /dev/null
> +++ b/libavfilter/af_astreamsync.c
> @@ -0,0 +1,204 @@
> +/*
> + * Copyright (c) 2011 Nicolas George <nicolas.george at normalesup.org>
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * Stream (de)synchronization filter
> + */
> +
> +#include <stdlib.h>
> +#include "libavcodec/avcodec.h"
not needed?
> +#include "libavutil/avstring.h"
> +#include "libavutil/eval.h"
> +#include "libswresample/swresample.h" // only for SWR_CH_MAX
> +#include "avfilter.h"
> +#include "internal.h"
> +
> +#define QUEUE_SIZE 16
> +
> +static const char * const var_names[] = {
> + "b1", "b2",
> + "s1", "s2",
> + "t1", "t2",
> + NULL
> +};
> +
> +enum var_name {
> + VAR_B1, VAR_B2,
> + VAR_S1, VAR_S2,
> + VAR_T1, VAR_T2,
> + VAR_NB
> +};
> +
> +struct astreamsync_context {
> + AVExpr *expr;
> + double var_values[VAR_NB];
> + struct {
> + AVFilterBufferRef *buf[QUEUE_SIZE];
> + unsigned tail, nb;
please provide some comment, or it will harder to read/understand this
code
> + } queue[2];
> + int req[2];
> + int next_out;
> + int eof;
maybe note that this is a bitmap, one bit for each input
pad/link (maybe using an array instead may help readability)
> +};
Nit++: AStreamSyncContext or ASyncContext or whatever for consistency
sake.
> +
> +static const char *default_expr = "t1-t2";
> +
> +static av_cold int init(AVFilterContext *ctx, const char *args0, void *opaque)
> +{
> + struct astreamsync_context *as = ctx->priv;
> + const char *expr = args0 ? args0 : default_expr;
> + int r, i;
> +
> + r = av_expr_parse(&as->expr, expr, var_names,
> + NULL, NULL, NULL, NULL, 0, ctx);
> + if (r < 0) {
> + av_log(ctx, AV_LOG_ERROR, "Error in expression \"%s\"\n", expr);
> + return r;
> + }
> + for (i = 0; i < 42; i++)
> + av_expr_eval(as->expr, as->var_values, NULL); /* exercize prng */
uh?
> + return 0;
> +}
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> + int i;
> + AVFilterFormats *formats;
> +
> + for (i = 0; i < 2; i++) {
> + formats = ctx->inputs[i]->in_formats;
> + avfilter_formats_ref(formats, &ctx->inputs[i]->out_formats);
> + avfilter_formats_ref(formats, &ctx->outputs[i]->in_formats);
> + formats = ctx->inputs[i]->in_packing;
> + avfilter_formats_ref(formats, &ctx->inputs[i]->out_packing);
> + avfilter_formats_ref(formats, &ctx->outputs[i]->in_packing);
> + formats = ctx->inputs[i]->in_chlayouts;
> + avfilter_formats_ref(formats, &ctx->inputs[i]->out_chlayouts);
> + avfilter_formats_ref(formats, &ctx->outputs[i]->in_chlayouts);
> + }
> + return 0;
> +}
> +
> +static int config_output(AVFilterLink *outlink)
> +{
> + return 0;
> +}
> +
> +static void send_out(AVFilterContext *ctx, int id)
nit: qid for making it more clear that id refers a queue (pad_id ->
pid or link_id -> lid would be fine as well)
> +{
> + struct astreamsync_context *as = ctx->priv;
> + AVFilterBufferRef *buf = as->queue[id].buf[as->queue[id].tail];
nit:
*queue = as->queue[id];
should ease readability:
as->queue[id].buf[as->queue[id].tail];
->
queue->buf[queue->tail];
> +
> + as->queue[id].buf[as->queue[id].tail] = NULL;
> + as->var_values[VAR_B1 + id]++;
> + as->var_values[VAR_S1 + id] += buf->audio->nb_samples;
> + if (buf->pts != AV_NOPTS_VALUE)
> + as->var_values[VAR_T1 + id] = av_q2d(ctx->inputs[id]->time_base) *
> + buf->pts;
> + as->var_values[VAR_T1 + id] += buf->audio->nb_samples /
> + (double)ctx->inputs[id]->sample_rate;
> + avfilter_filter_samples(ctx->outputs[id], buf);
> + as->queue[id].nb--;
> + as->queue[id].tail = (as->queue[id].tail + 1) % QUEUE_SIZE;
> + if (as->req[id])
> + as->req[id]--;
> +}
> +
> +static void send_next(AVFilterContext *ctx)
> +{
> + struct astreamsync_context *as = ctx->priv;
> + int i;
> +
> + while (1) {
> + if (!as->queue[as->next_out].nb)
> + break;
> + send_out(ctx, as->next_out);
> + if (!as->eof)
> + as->next_out = av_expr_eval(as->expr, as->var_values, NULL) >= 0;
> + }
> + for (i = 0; i < 2; i++)
> + if (as->queue[i].nb == QUEUE_SIZE)
> + send_out(ctx, i);
> +}
> +
> +static int request_frame(AVFilterLink *outlink)
> +{
> + AVFilterContext *ctx = outlink->src;
> + struct astreamsync_context *as = ctx->priv;
> + int id = outlink == ctx->outputs[1];
> +
> + as->req[id]++;
> + while (as->req[id] && !(as->eof & (1 << id))) {
> + if (as->queue[as->next_out].nb) {
> + send_next(ctx);
> + } else {
> + as->eof |= 1 << as->next_out;
> + avfilter_request_frame(ctx->inputs[as->next_out]);
> + if (as->eof & (1 << as->next_out))
> + as->next_out = !as->next_out;
> + }
> + }
> + return 0;
> +}
> +
> +static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
> +{
> + AVFilterContext *ctx = inlink->dst;
> + struct astreamsync_context *as = ctx->priv;
> + int id = inlink == ctx->inputs[1];
> +
> + as->queue[id].buf[(as->queue[id].tail + as->queue[id].nb++) % QUEUE_SIZE] =
> + insamples;
circular buffer overflow? shouldn't you check that the buffer is not
already filled (and in that case maybe release memory)?
> + as->eof &= ~(1 << id);
> + send_next(ctx);
> +}
> +
> +AVFilter avfilter_af_astreamsync = {
> + .name = "astreamsync",
> + .description = NULL_IF_CONFIG_SMALL("Copy two streams of audio data "
> + "in a configurable order"),
Nit: missing final dot.
--
FFmpeg = Fabulous Fiendish Magnificient Portable Elfic Gadget
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