[FFmpeg-devel] [PATCH] lavfi: add asendcmd and sendcmd filters
Stefano Sabatini
stefasab at gmail.com
Tue Aug 14 20:55:56 CEST 2012
On date Tuesday 2012-08-14 15:03:24 +0200, Nicolas George encoded:
> L'octidi 28 thermidor, an CCXX, Stefano Sabatini a écrit :
> > ---
> > doc/filters.texi | 70 ++++++++++
> > libavfilter/Makefile | 2 +
> > libavfilter/allfilters.c | 2 +
> > libavfilter/f_sendcmd.c | 332 ++++++++++++++++++++++++++++++++++++++++++++++
> > 4 files changed, 406 insertions(+), 0 deletions(-)
> > create mode 100644 libavfilter/f_sendcmd.c
> >
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index 763085c..ae5af7c 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -4064,6 +4064,76 @@ tools.
> >
> > Below is a description of the currently available multimedia filters.
> >
> > + at section asendcmd, sendcmd
> > +
> > +Send commands to filters in the filtergraph.
> > +
> > +These filters read commands to be sent to other filters in the
> > +filtergraph.
> > +
>
> > + at code{asendcmd} must be inserted between two audio filters,
> > + at code{sendcmd} must be inserted between two video filters, but apart
> > +from that they act the same.
>
> If I undestand correctly, the placement of the filters in the graph only
> affect the time they see on the frames, right?
Yes.
>
> > +
> > +The specification of commands can be specified in the filter arguments
> > +with the @var{commands} option, or in a file specified with the
> > + at var{filename} option.
> > +
>
> > +Commands are sent the first time when a frame with time greater or
> > +equal to the specified command time is processed by the filter.
>
> Hum. It works for encoding, but not for interactive playback where seeks
> backwards happen. A lot of filters have that problem, though.
Well, I suppose we could detect when the time goes back in case t2 <=
t1, and seek back to the first command with time >= t2.
[...]
> > +/**
> > + * @file
> > + * send commands filter
> > + */
> > +
> > +#include "libavutil/avstring.h"
> > +#include "libavutil/file.h"
> > +#include "libavutil/opt.h"
> > +#include "libavutil/parseutils.h"
> > +#include "avfilter.h"
> > +#include "internal.h"
> > +#include "avfiltergraph.h"
> > +#include "audio.h"
> > +#include "video.h"
> > +
> > +typedef struct {
> > + char *buf; ///< allocated buffer
> > + char *target, *command, *arg;
>
> > + double t;
>
> Any reason to use a double and not just an int64_t in AV_TIME_BASE or in
> link->time_base? Floats are tricky.
Changed to 1/1000000 units.
[...]
> > +static const AVOption sendcmd_options[]= {
> > + { "commands", "set commands", OFFSET(commands_str), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0 },
> > + { "c", "set commands", OFFSET(commands_str), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0 },
> > + { "filename", "set commands file", OFFSET(commands_filename), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0 },
> > + { "f", "set commands file", OFFSET(commands_filename), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0 },
> > + {NULL},
> > +};
> > +
> > +AVFILTER_DEFINE_CLASS(sendcmd);
> > +
>
> > +#define DELIMS " \f\t"
>
> What happens if your lines are terminated by \r\n?
Syntax error (a line containing only "\r" doesn't contain enough
information.
[...]
> > +static int parse_commands(Command **cmds, int *nb_cmds,
> > + const char *cmds_buf, size_t cmds_bufsize,
> > + void *log_ctx)
> > +{
> > + char *line = NULL;
> > + size_t line_size = 0;
> > + int line_count;
> > + int ret, n = 0;
> > + const char *p = cmds_buf;
> > + const char *pend = cmds_buf + cmds_bufsize;
> > +
> > + *nb_cmds = 0;
> > + if (!p)
> > + return 0;
> > + for (line_count = 0; *p; line_count++) {
> > + Command cmd;
> > + int i = 0;
> > +
>
> > + /* skip empty lines && # comments */
>
> I believe this comment goes a few lines later.
Yes.
> > + while (p[i] != '\n' && p+i < pend)
> > + i++;
> > + line_size = i;
>
> It makes multiline commands impossible, does it not?
Yes. At the moment I don't know how to support commands which spans
for more than one line. I suppose we could make use of some form of
\n escaping.
> > +
> > + if (*p == '\n' || *p == '#') {
> > + p += line_size+1;
> > + continue;
> > + }
>
> What happens if a line starts with a space and then a comment?
It will abort since the line doesn't contain a command (# not at the
begin of the line are not treated as comments).
> > +
> > + line = av_realloc_f(line, line_size+1, 1);
> > + if (!line) {
> > + ret = AVERROR(ENOMEM);
> > + goto end;
> > + }
> > + memcpy(line, p, line_size);
> > + line[line_size] = 0;
> > +
> > + if ((ret = parse_command(&cmd, line, log_ctx)) < 0) {
> > + av_log(log_ctx, AV_LOG_ERROR,
> > + "Error occurred parsing line %d: %s\n", line_count, line);
> > + goto end;
> > + }
> > +
> > + /* (re)allocate commands array if required*/
> > + if (*nb_cmds == n) {
> > + n = FFMAX(16, 2*n);
> > + *cmds = av_realloc_f(*cmds, n, 2*sizeof(Command));
>
> > + if (!*cmds) {
> > + ret = AVERROR(ENOMEM);
> > + }
>
> It looks like there is a goto missing, or *cmds will be dereferenced anyway.
Well spotted.
>
> > + }
> > + (*cmds)[(*nb_cmds)++] = cmd;
> > + p += line_size+1;
> > + }
> > +
> > +end:
> > + av_free(line);
> > + return ret;
> > +}
> > +
> > +static av_cold int init(AVFilterContext *ctx, const char *args)
> > +{
> > + SendCmdContext *sendcmd = ctx->priv;
> > + int ret, i;
> > + char *buf;
> > + size_t bufsize;
> > +
> > + sendcmd->class = &sendcmd_class;
> > + av_opt_set_defaults(sendcmd);
> > +
> > + if ((ret = av_set_options_string(sendcmd, args, "=", ":")) < 0)
> > + return ret;
> > +
> > + if (sendcmd->commands_filename && sendcmd->commands_str) {
> > + av_log(ctx, AV_LOG_ERROR,
> > + "Only one of the filename or commands options must be specified\n");
> > + return AVERROR(EINVAL);
> > + }
> > +
> > + if (sendcmd->commands_filename) {
> > + ret = av_file_map(sendcmd->commands_filename,
> > + &sendcmd->commands_file_buf,
> > + &sendcmd->commands_file_bufsize, 0, ctx);
> > + if (ret < 0)
> > + return ret;
> > + buf = sendcmd->commands_file_buf;
> > + bufsize = sendcmd->commands_file_bufsize;
> > + } else {
> > + buf = sendcmd->commands_str;
> > + bufsize = strlen(sendcmd->commands_str) + 1;
> > + }
> > +
> > + if ((ret = parse_commands(&sendcmd->commands, &sendcmd->nb_commands,
> > + buf, bufsize, ctx)) < 0)
> > + return ret;
> > +
>
> > + qsort(sendcmd->commands, sendcmd->nb_commands, sizeof(Command), cmp_commands);
>
> The user can specify several commands for the same time, and the order may
> be relevant: a stable sort would be required.
I don't know if we have already a mergesort implementation in our
codebase or if I should hack it.
> > +
> > + av_log(ctx, AV_LOG_DEBUG, "Parsed commands:\n");
> > + for (i = 0; i < sendcmd->nb_commands; i++) {
> > + Command cmd = sendcmd->commands[i];
> > + av_log(ctx, AV_LOG_DEBUG, "target:%s time:%f command:%s arg:%s\n",
> > + cmd.target, cmd.t, cmd.command, cmd.arg);
> > + }
> > +
> > + return 0;
> > +}
> > +
[...]
> > +static int end_frame(AVFilterLink *inlink)
> > +{
> > + inlink->cur_buf = NULL;
> > + return ff_end_frame(inlink->dst->outputs[0]);
> > +}
>
> Any reason not to clear cur_buf in process_frame?
Good idea, fixed.
[...]
> That is an useful feature, thanks.
Thanks (I implemented it mainly as a testing device, but can be useful
in many reconfiguration scenarios).
Patch updated. Todo:
1. stable sort of commands
2. ecaping of newlines (useful for commands which contains newlines in
the argument
3. silly \r\n line ending support??
4. more meaningful drawtext examples
--
FFmpeg = Fantastic & Forgiving Meaningless Programmable Elegant Gadget
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