On 2019-02-21 8:47 a.m., Strahinja Radman wrote:
*From: *Michael Bachmann <mailto:[email protected]>
*Sent: *21 February 2019 13:02
*To: *[email protected] <mailto:[email protected]>
*Subject: *[Libav-user] Getting resulting width and height from scale filter
Is there a way to get the resulting width and height from a scale
filter, so i can setup the Encoding-AVCodecContext correctly (with width
and height)?
Here's my init filter method, which gets feeded with the filter
description "scale=-1:'min(720,iw)'":
int FFMPEGCommands::init_filters(const char *filters_descr, int width,
int height, int streamFrameRate) {
char args[512];
int ret = 0;
const AVFilter *buffersrc = avfilter_get_by_name("buffer");
const AVFilter *buffersink = avfilter_get_by_name("buffersink");
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
AVRational time_base = { 1, streamFrameRate };
//AVRational time_base =
fmt_ctx->streams[video_stream_index]->time_base;
enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P,
AV_PIX_FMT_NONE };
filter_graph = avfilter_graph_alloc();
if (!outputs || !inputs || !filter_graph) {
ret = AVERROR(ENOMEM);
goto end;
}
/* buffer video source: the decoded frames from the decoder will be
inserted here. */
snprintf(args, sizeof(args),
"video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
width, height, STREAM_PIX_FMT,
time_base.num, time_base.den,
0, 1);
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
goto end;
}
/* buffer video sink: to terminate the filter chain. */
ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
NULL, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
goto end;
}
ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
goto end;
}
/*
* Set the endpoints for the filter graph. The filter_graph will
* be linked to the graph described by filters_descr.
*/
/*
* The buffer source output must be connected to the input pad of
* the first filter described by filters_descr; since the first
* filter input label is not specified, it is set to "in" by
* default.
*/
outputs->name = av_strdup("in");
outputs->filter_ctx = buffersrc_ctx;
outputs->pad_idx = 0;
outputs->next = NULL;
/*
* The buffer sink input must be connected to the output pad of
* the last filter described by filters_descr; since the last
* filter output label is not specified, it is set to "out" by
* default.
*/
inputs->name = av_strdup("out");
inputs->filter_ctx = buffersink_ctx;
inputs->pad_idx = 0;
inputs->next = NULL;
if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
&inputs, &outputs, NULL)) < 0)
goto end;
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
goto end;
end:
avfilter_inout_free(&inputs);
avfilter_inout_free(&outputs);
return ret;
}
The info you are seeking should be available here
filter_ctx.buffersink_ctx->inputs[0]->w for width and
filter_ctx.buffersink_ctx->inputs[0]->h for height.
From avfilter.h: "Applications must not normally access the link
structure directly. Use the buffersrc and buffersink API instead."
The buffersink API (described in buffersink.h) shows that
av_buffersink_get_w and av_buffersink_get_h can be used by passing in
buffersink_ctx.
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--
Philippe Gorley
Free Software Consultant | Montréal, Qc
Savoir-faire Linux
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