[FFmpeg-devel] [PATCH v6] lavf/flv: Add XV (Xunlei Video) Support. Fixes ticket #3720

[Michael Niedermayer]

On Tue, Apr 09, 2019 at 11:50:16PM +0530, Shivam Goyal wrote:
> lavf/flv: Add XV (Xunlei Video) Support.
> 
> Fixes ticket #3720.
> 
> 
> 

>  Changelog                |    1 
>  libavformat/Makefile     |    1 
>  libavformat/allformats.c |    1 
>  libavformat/flvdec.c     |   86 +++++++++++++++++++++++++++++++++++++++++++++++
>  libavformat/version.h    |    2 -
>  5 files changed, 90 insertions(+), 1 deletion(-)
> c221c019d4dcd7063828c54567b8fc7c905b211b  added_xv_support_v6.patch
> From 605dc262abf948813c26d58f51d5e2d7f498d9cd Mon Sep 17 00:00:00 2001
> From: Shivam Goyal <shivgo at iitk.ac.in>
> Date: Tue, 9 Apr 2019 23:36:27 +0530
> Subject: [PATCH] lavf/flv: Add XV (Xunlei Video) Support. Fixes ticket #3720.
> 
> ---
>  Changelog                |  1 +
>  libavformat/Makefile     |  1 +
>  libavformat/allformats.c |  1 +
>  libavformat/flvdec.c     | 86 ++++++++++++++++++++++++++++++++++++++++
>  libavformat/version.h    |  2 +-
>  5 files changed, 90 insertions(+), 1 deletion(-)
> 
> diff --git a/Changelog b/Changelog
> index 8c866cd0c2..8caaab53c2 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -22,6 +22,7 @@ version <next>:
>  - removed libndi-newtek
>  - agm decoder
>  - KUX demuxer
> +- XV (Xunlei Video) demuxer
>  
>  
>  version 4.1:
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 99be60d184..e090c051f1 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -561,6 +561,7 @@ OBJS-$(CONFIG_WV_MUXER)                  += wvenc.o wv.o apetag.o img2.o
>  OBJS-$(CONFIG_XA_DEMUXER)                += xa.o
>  OBJS-$(CONFIG_XBIN_DEMUXER)              += bintext.o sauce.o
>  OBJS-$(CONFIG_XMV_DEMUXER)               += xmv.o
> +OBJS-$(CONFIG_XV_DEMUXER)                += flvdec.o
>  OBJS-$(CONFIG_XVAG_DEMUXER)              += xvag.o
>  OBJS-$(CONFIG_XWMA_DEMUXER)              += xwma.o
>  OBJS-$(CONFIG_YOP_DEMUXER)               += yop.o
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index d316a0529a..b499186071 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -456,6 +456,7 @@ extern AVOutputFormat ff_wv_muxer;
>  extern AVInputFormat  ff_xa_demuxer;
>  extern AVInputFormat  ff_xbin_demuxer;
>  extern AVInputFormat  ff_xmv_demuxer;
> +extern AVInputFormat  ff_xv_demuxer;
>  extern AVInputFormat  ff_xvag_demuxer;
>  extern AVInputFormat  ff_xwma_demuxer;
>  extern AVInputFormat  ff_yop_demuxer;
> diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
> index b531a39adc..a56f5b448a 100644
> --- a/libavformat/flvdec.c
> +++ b/libavformat/flvdec.c
> @@ -127,6 +127,19 @@ static int kux_probe(const AVProbeData *p)
>      return 0;
>  }
>  
> +static int xv_probe(const AVProbeData *p)
> +{
> +    const uint8_t *d = p->buf;
> +
> +    if (d[0] == 'X' &&
> +        d[1] == 'L' &&
> +        d[2] == 'V' &&
> +        d[3] == 'F') {
> +        return AVPROBE_SCORE_EXTENSION + 1;
> +    }
> +    return 0;
> +}
> +
>  static void add_keyframes_index(AVFormatContext *s)
>  {
>      FLVContext *flv   = s->priv_data;
> @@ -459,6 +472,12 @@ static int parse_keyframes_index(AVFormatContext *s, AVIOContext *ioc, int64_t m
>          }
>      }
>  
> +    if (!strcmp(s->iformat->name , "xv")) {
> +        for (i = 0; i < FFMIN(2,fileposlen); i++) {
> +            filepositions[i] += 0x200000;
> +        }
> +    }
> +
>      if (timeslen == fileposlen && fileposlen>1 && max_pos <= filepositions[0]) {
>          for (i = 0; i < FFMIN(2,fileposlen); i++) {
>              flv->validate_index[i].pos = filepositions[i];
> @@ -783,6 +802,52 @@ static int flv_read_header(AVFormatContext *s)
>      return 0;
>  }
>  
> +static int xv_read_header(AVFormatContext *s)
> +{
> +    int flags;
> +    FLVContext *xv = s->priv_data;
> +    AVIOContext *ic = s->pb;
> +    int offset;
> +    int rot;
> +    int i;
> +    int64_t pos;
> +
> +    //Find the rot value for rotating the bytes
> +    avio_skip(ic, 0x200000);
> +    rot = 0x46 - avio_r8(ic);
> +
> +    avio_skip(ic, 3);
> +
> +    flags = (avio_r8(ic) + rot) & 0xff;
> +
> +    xv->missing_streams = flags & (FLV_HEADER_FLAG_HASVIDEO | FLV_HEADER_FLAG_HASAUDIO);
> +
> +    s->ctx_flags |= AVFMTCTX_NOHEADER;
> +
> +    offset = ((avio_r8(ic) + rot & 0xff) << 24 |
> +              (avio_r8(ic) + rot & 0xff) << 16 |
> +              (avio_r8(ic) + rot & 0xff) << 8 |
> +              (avio_r8(ic) + rot & 0xff)) + 0x200000;
> +
> +    avio_seek(ic, offset + 4, SEEK_SET);
> +
> +
> +    // Will modify the current buffer, as only
> +    // the bytes from 0x200000 to 0x200400 are needed to decode
> +    pos = ic->pos + ic->buf_ptr - ic->buf_end;
> +    for (i = 0; i < 0x400; i++) {
> +        if (pos >= 0x200400) break;
> +        ic->buf_ptr[i] = (ic->buf_ptr[i] + rot) & 0xff;
> +        pos++;
> +    }

the demuxer should not manipulate the protocols /avio internal buffer.
This would make the demuxer depend on how this buffer is implemented.
Also the data that needs changes may not be in the buffer but be read
later i think-
It would be quite annoying for maintaince if changing the internal
AVIO code would require updating the implementations of demuxers

[...]


-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
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