[FFmpeg-devel] [PATCH] avformat/dhav: also support ZLAV packets

[Zhao Zhili]

Hi Michael,

> On Oct 24, 2020, at 8:32 AM, Michael Keeley <mike at keeley.net.nz> wrote:
> 
> Some DVRs (e.g. D7008FH made by Zhuhai Ltd) output the same format .dav file,
> but use ZLAV/zlav tags to delimit the packets instead of DHAV/dhav.

Zhuhai Ltd doesn't look like the real company name. I didn't find much information
about D7008FH. Could you share more informations so I can help figure out the product
model and vendor? Of course, if such information matters.

> 
> Signed-off-by: Michael Keeley <mike at keeley.net.nz>
> ---
> Changelog             |  1 +
> libavformat/dhav.c    | 31 ++++++++++++++++++++++---------
> libavformat/version.h |  2 +-
> 3 files changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/Changelog b/Changelog
> index 21a4be731b..8e289733e2 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -37,6 +37,7 @@ version <next>:
> - Cintel RAW decoder
> - VDPAU accelerated VP9 10/12bit decoding
> - afreqshift and aphaseshift filters
> +- Add ZLAV format to DHAV demuxer
> 
> 
> version 4.3:
> diff --git a/libavformat/dhav.c b/libavformat/dhav.c
> index 79afe9be03..e2f3c40065 100644
> --- a/libavformat/dhav.c
> +++ b/libavformat/dhav.c
> @@ -1,5 +1,5 @@
> /*
> - * DHAV demuxer
> + * DHAV/ZLAV demuxer
>  *
>  * Copyright (c) 2018 Paul B Mahol
>  *
> @@ -57,7 +57,7 @@ static int dhav_probe(const AVProbeData *p)
>     if (!memcmp(p->buf, "DAHUA", 5))
>         return AVPROBE_SCORE_MAX;
> 
> -    if (memcmp(p->buf, "DHAV", 4))
> +    if (memcmp(p->buf, "DHAV", 4) != 0 && memcmp(p->buf, "ZLAV", 4) != 0)
>         return 0;
> 
>     if (p->buf[4] == 0xf0 ||
> @@ -163,6 +163,19 @@ static int parse_ext(AVFormatContext *s, int length)
>     return 0;
> }
> 
> +static int read_start_tag(AVIOContext *pb)
> +{
> +    unsigned int start_tag = avio_rl32(pb);
> +    return start_tag == MKTAG('D','H','A','V') || start_tag == MKTAG('Z','L','A','V');
> +}
> +
> +static int read_end_tag(AVIOContext *pb)
> +{
> +    unsigned int end_tag = avio_rl32(pb);
> +    return end_tag == MKTAG('d','h','a','v') || end_tag == MKTAG('z','l','a','v');
> +}
> +
> +
> static int read_chunk(AVFormatContext *s)
> {
>     DHAVContext *dhav = s->priv_data;
> @@ -173,11 +186,11 @@ static int read_chunk(AVFormatContext *s)
>     if (avio_feof(s->pb))
>         return AVERROR_EOF;
> 
> -    if (avio_rl32(s->pb) != MKTAG('D','H','A','V')) {
> +    if (!read_start_tag(s->pb)) {
>         dhav->last_good_pos += 0x8000;
>         avio_seek(s->pb, dhav->last_good_pos, SEEK_SET);
> 
> -        while (avio_rl32(s->pb) != MKTAG('D','H','A','V')) {
> +        while (!read_start_tag(s->pb)) {
>             if (avio_feof(s->pb))
>                 return AVERROR_EOF;
>             dhav->last_good_pos += 0x8000;
> @@ -247,7 +260,7 @@ static int64_t get_duration(AVFormatContext *s)
>         return 0;
> 
>     avio_seek(s->pb, avio_size(s->pb) - 8, SEEK_SET);
> -    if (avio_rl32(s->pb) == MKTAG('d','h','a','v')) {
> +    if (read_end_tag(s->pb)) {
>         int seek_back = avio_rl32(s->pb);
> 
>         avio_seek(s->pb, -seek_back, SEEK_CUR);
> @@ -281,12 +294,12 @@ static int dhav_read_header(AVFormatContext *s)
>         avio_skip(s->pb, 0x400 - 5);
>         dhav->last_good_pos = avio_tell(s->pb);
>     } else {
> -        if (!memcmp(signature, "DHAV", 4)) {
> +        if (memcmp(signature, "DHAV", 4) == 0 || memcmp(signature, "ZLAV", 4) == 0) {
>             avio_seek(s->pb, -5, SEEK_CUR);
>             dhav->last_good_pos = avio_tell(s->pb);
>         } else if (s->pb->seekable) {
>             avio_seek(s->pb, avio_size(s->pb) - 8, SEEK_SET);
> -            while (avio_rl32(s->pb) == MKTAG('d','h','a','v')) {
> +            while (read_end_tag(s->pb)) {
>                 int seek_back;
> 
>                 seek_back = avio_rl32(s->pb) + 8;
> @@ -409,7 +422,7 @@ retry:
>     stream_index = dhav->type == 0xf0 ? dhav->audio_stream_index : dhav->video_stream_index;
>     if (stream_index < 0) {
>         avio_skip(s->pb, ret);
> -        if (avio_rl32(s->pb) == MKTAG('d','h','a','v'))
> +        if (read_end_tag(s->pb))
>             avio_skip(s->pb, 4);
>         goto retry;
>     }
> @@ -425,7 +438,7 @@ retry:
>     if (pkt->stream_index >= 0)
>         pkt->pts = get_pts(s, pkt->stream_index);
>     pkt->pos = dhav->last_good_pos;
> -    if (avio_rl32(s->pb) == MKTAG('d','h','a','v'))
> +    if (read_end_tag(s->pb))
>         avio_skip(s->pb, 4);
> 
>     return ret;
> diff --git a/libavformat/version.h b/libavformat/version.h
> index 86e0a232ee..7853068649 100644
> --- a/libavformat/version.h
> +++ b/libavformat/version.h
> @@ -32,7 +32,7 @@
> // Major bumping may affect Ticket5467, 5421, 5451(compatibility with Chromium)
> // Also please add any ticket numbers that you believe might be affected here
> #define LIBAVFORMAT_VERSION_MAJOR  58
> -#define LIBAVFORMAT_VERSION_MINOR  62
> +#define LIBAVFORMAT_VERSION_MINOR  63
> #define LIBAVFORMAT_VERSION_MICRO 100
> 
> #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
> -- 
> 2.25.1
> 
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