[FFmpeg-devel] [PATCH 3/4] avformat/hashenc: add option to create hash per stream

[Paul B Mahol]

I think better thing to do is to add streamhash muxer instead of doing
it in hash muxer.

On 8/11/19, Moritz Barsnick <barsnick at gmx.net> wrote:
> Non-frame based muxers only, the frame based ones are already per
> stream.
>
> Signed-off-by: Moritz Barsnick <barsnick at gmx.net>
> ---
>  doc/muxers.texi       |  5 +++++
>  libavformat/hashenc.c | 41 +++++++++++++++++++++++++++++------------
>  2 files changed, 34 insertions(+), 12 deletions(-)
>
> diff --git a/doc/muxers.texi b/doc/muxers.texi
> index bc38cf6029..34ca7f07cb 100644
> --- a/doc/muxers.texi
> +++ b/doc/muxers.texi
> @@ -511,6 +511,11 @@ Supported values include @code{MD5}, @code{murmur3},
> @code{RIPEMD128},
>  @code{SHA224}, @code{SHA256} (default), @code{SHA512/224},
> @code{SHA512/256},
>  @code{SHA384}, @code{SHA512}, @code{CRC32} and @code{adler32}.
>
> + at item per_stream @var{bool}
> +Whether to calculate a hash per stream, instead of combined over all
> +packets' payload. Each stream's hash is prefixed with its stream index.
> +Default is @code{false}.
> +
>  @end table
>
>  @subsection Examples
> diff --git a/libavformat/hashenc.c b/libavformat/hashenc.c
> index 96e00f580c..394b8a0fce 100644
> --- a/libavformat/hashenc.c
> +++ b/libavformat/hashenc.c
> @@ -31,6 +31,7 @@ struct HashContext {
>      const AVClass *avclass;
>      struct AVHashContext **hashes;
>      char *hash_name;
> +    int per_stream;
>      int format_version;
>  };
>
> @@ -40,10 +41,13 @@ struct HashContext {
>      { "hash", "set hash to use", OFFSET(hash_name), AV_OPT_TYPE_STRING,
> {.str = defaulttype}, 0, 0, ENC }
>  #define FORMAT_VERSION_OPT \
>      { "format_version", "file format version", OFFSET(format_version),
> AV_OPT_TYPE_INT, {.i64 = 2}, 1, 2, ENC }
> +#define PER_STREAM_OPT \
> +    { "per_stream", "whether to calculate a hash per stream",
> OFFSET(per_stream), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, ENC }
>
>  #if CONFIG_HASH_MUXER
>  static const AVOption hash_options[] = {
>      HASH_OPT("sha256"),
> +    PER_STREAM_OPT,
>      { NULL },
>  };
>  #endif
> @@ -59,6 +63,7 @@ static const AVOption framehash_options[] = {
>  #if CONFIG_MD5_MUXER
>  static const AVOption md5_options[] = {
>      HASH_OPT("md5"),
> +    PER_STREAM_OPT,
>      { NULL },
>  };
>  #endif
> @@ -74,39 +79,51 @@ static const AVOption framemd5_options[] = {
>  #if CONFIG_HASH_MUXER || CONFIG_MD5_MUXER
>  static int hash_write_header(struct AVFormatContext *s)
>  {
> -    int res;
> +    int i, res;
>      struct HashContext *c = s->priv_data;
> -    c->hashes = av_malloc_array(1, sizeof(c->hashes));
> +    int num_hashes = c->per_stream ? s->nb_streams : 1;
> +    c->hashes = av_malloc_array(num_hashes, sizeof(c->hashes));
>      if (!c->hashes)
>          return AVERROR(ENOMEM);
> -    res = av_hash_alloc(&c->hashes[0], c->hash_name);
> -    if (res < 0) {
> -        av_freep(&c->hashes);
> -        return res;
> +    for (i = 0; i < num_hashes; i++) {
> +    res = av_hash_alloc(&c->hashes[i], c->hash_name);
> +    if (res < 0)
> +        goto err;
> +    av_hash_init(c->hashes[i]);
>      }
> -    av_hash_init(c->hashes[0]);
>      return 0;
> +err:
> +    for (int j = 0; j < i; j++)
> +        av_hash_freep(&c->hashes[j]);
> +    av_freep(&c->hashes);
> +    return res;
>  }
>
>  static int hash_write_packet(struct AVFormatContext *s, AVPacket *pkt)
>  {
>      struct HashContext *c = s->priv_data;
> -    av_hash_update(c->hashes[0], pkt->data, pkt->size);
> +    av_hash_update(c->hashes[c->per_stream ? pkt->stream_index : 0],
> pkt->data, pkt->size);
>      return 0;
>  }
>
>  static int hash_write_trailer(struct AVFormatContext *s)
>  {
>      struct HashContext *c = s->priv_data;
> +    int num_hashes = c->per_stream ? s->nb_streams : 1;
> +    for (int i = 0; i < num_hashes; i++) {
>      char buf[AV_HASH_MAX_SIZE*2+128];
> -    snprintf(buf, sizeof(buf) - 200, "%s=",
> av_hash_get_name(c->hashes[0]));
> -
> -    av_hash_final_hex(c->hashes[0], buf + strlen(buf), sizeof(buf) -
> strlen(buf));
> +    if (c->per_stream) {
> +        snprintf(buf, sizeof(buf) - 200, "%d,%s=", i,
> av_hash_get_name(c->hashes[i]));
> +    } else {
> +        snprintf(buf, sizeof(buf) - 200, "%s=",
> av_hash_get_name(c->hashes[i]));
> +    }
> +    av_hash_final_hex(c->hashes[i], buf + strlen(buf), sizeof(buf) -
> strlen(buf));
>      av_strlcatf(buf, sizeof(buf), "\n");
>      avio_write(s->pb, buf, strlen(buf));
>      avio_flush(s->pb);
>
> -    av_hash_freep(&c->hashes[0]);
> +    av_hash_freep(&c->hashes[i]);
> +    }
>      av_freep(&c->hashes);
>      return 0;
>  }
> --
> 2.20.1
>
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