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

[Vignesh Venkatasubramanian]

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?

> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Concerning the gods, I have no means of knowing whether they exist or not
> or of what sort they may be, because of the obscurity of the subject, and
> the brevity of human life -- Protagoras
>
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-- 
Vignesh