[FFmpeg-devel] [PATCH] lavf: Add support for WebM Live Muxing

[Michael Niedermayer]

On Mon, Apr 06, 2015 at 11:19:36AM -0700, Vignesh Venkatasubramanian wrote:
> On Sat, Apr 4, 2015 at 3:38 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Mon, Mar 30, 2015 at 02:46:10PM -0700, Vignesh Venkatasubramanian wrote:
> >> This patch adds support for WebM Live Muxing by adding a new WebM
> >> Chunk muxer. It writes out live WebM Chunks which can be used for
> >> playback using Live DASH Clients.
> >>
> >> Please see muxers.texi for sample usage.
> >
> > [...]
> >
> >> diff --git a/libavformat/version.h b/libavformat/version.h
> >> index a183d7f..ff85227 100644
> >> --- a/libavformat/version.h
> >> +++ b/libavformat/version.h
> >> @@ -30,7 +30,7 @@
> >>  #include "libavutil/version.h"
> >>
> >>  #define LIBAVFORMAT_VERSION_MAJOR 56
> >> -#define LIBAVFORMAT_VERSION_MINOR  26
> >> +#define LIBAVFORMAT_VERSION_MINOR  27
> >>  #define LIBAVFORMAT_VERSION_MICRO 101
> >>
> >>  #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
> >> diff --git a/libavformat/webm_chunk.c b/libavformat/webm_chunk.c
> >> new file mode 100644
> >> index 0000000..48ea6f0
> >> --- /dev/null
> >> +++ b/libavformat/webm_chunk.c
> >> @@ -0,0 +1,262 @@
> >> +/*
> >> + * Copyright (c) 2015, Vignesh Venkatasubramanian
> >> + *
> >> + * 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
> >> + * Lesser 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 WebM Chunk Muxer
> >> + * The chunk muxer enables writing WebM Live chunks where there is a header
> >> + * chunk, followed by data chunks where each Cluster is written out as a Chunk.
> >> + */
> >> +
> >> +#include <float.h>
> >> +#include <time.h>
> >> +
> >> +#include "avformat.h"
> >> +#include "avio.h"
> >> +#include "internal.h"
> >> +
> >> +#include "libavutil/avassert.h"
> >> +#include "libavutil/log.h"
> >> +#include "libavutil/opt.h"
> >> +#include "libavutil/avstring.h"
> >> +#include "libavutil/parseutils.h"
> >> +#include "libavutil/mathematics.h"
> >> +#include "libavutil/time.h"
> >> +#include "libavutil/time_internal.h"
> >> +#include "libavutil/timestamp.h"
> >> +
> >> +typedef struct WebMChunkContext {
> >> +    const AVClass *class;
> >> +    int chunk_start_index;
> >> +    char *header_filename;
> >> +    int chunk_duration;
> >> +    int chunk_count;
> >> +    int chunk_index;
> >> +    uint64_t duration_written;
> >> +    int prev_pts;
> >> +    AVOutputFormat *oformat;
> >> +    AVFormatContext *avf;
> >> +} WebMChunkContext;
> >> +
> >> +static int chunk_mux_init(AVFormatContext *s)
> >> +{
> >> +    WebMChunkContext *wc = s->priv_data;
> >> +    AVFormatContext *oc;
> >> +    int ret;
> >> +
> >> +    ret = avformat_alloc_output_context2(&wc->avf, wc->oformat, NULL, NULL);
> >> +    if (ret < 0)
> >> +        return ret;
> >> +    oc = wc->avf;
> >> +
> >> +    oc->interrupt_callback = s->interrupt_callback;
> >> +    oc->max_delay          = s->max_delay;
> >> +    av_dict_copy(&oc->metadata, s->metadata, 0);
> >> +
> >> +    oc->priv_data = av_mallocz(oc->oformat->priv_data_size);
> >> +    if (!oc->priv_data) {
> >> +        avio_close(oc->pb);
> >> +        return AVERROR(ENOMEM);
> >> +    }
> >> +    *(const AVClass**)oc->priv_data = oc->oformat->priv_class;
> >> +    av_opt_set_defaults(oc->priv_data);
> >> +    av_opt_set_int(oc->priv_data, "dash", 1, 0);
> >> +    av_opt_set_int(oc->priv_data, "cluster_time_limit", wc->chunk_duration, 0);
> >> +    av_opt_set_int(oc->priv_data, "live", 1, 0);
> >> +
> >
> >> +    oc->streams = s->streams;
> >> +    oc->nb_streams = s->nb_streams;
> >
> > why doesnt the code use avformat_new_stream() and avcodec_copy_context()
> > see hlsenc/segment muxers for examples
> >
> > or is there a reason why this would not work or be hard ?
> >
> 
> it seems unnecessary to make a copy of the stream and codec context
> when it can be used safely within this file without duplication. is
> there something wrong with that line of thought?

well, it feels a bit odd but if you prefer it? ill push it that way

Thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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