Re: [FFmpeg-devel] [PATCH v8 4/5] ogg/vorbis: implement header packet skip in chained ogg bitstreams.

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Romain Beauxis:
> Le ven. 30 mai 2025 à 19:44, Andreas Rheinhardt
> <andreas.rheinhardt@outlook.com> a écrit :
>>
>> Romain Beauxis:
>>> ---
>>>  libavcodec/vorbis_parser.h                 | 11 ++++
>>>  libavcodec/vorbisdec.c                     | 75 +++++++++++++---------
>>>  libavformat/oggparsevorbis.c               | 67 ++++++++++++++++++-
>>>  tests/ref/fate/ogg-vorbis-chained-meta.txt |  3 -
>>>  tests/ref/fate/trac-2739.txt               |  4 +-
>>>  5 files changed, 121 insertions(+), 39 deletions(-)
>>>
>>> diff --git a/libavcodec/vorbis_parser.h b/libavcodec/vorbis_parser.h
>>> index 789932ac49..b176fe536c 100644
>>> --- a/libavcodec/vorbis_parser.h
>>> +++ b/libavcodec/vorbis_parser.h
>>> @@ -30,6 +30,17 @@
>>>
>>>  typedef struct AVVorbisParseContext AVVorbisParseContext;
>>>
>>> +/**
>>> + * Used by the vorbis parser to pass new chained stream headers
>>> + * as extradata.
>>> + */
>>> +typedef struct vorbis_new_extradata {
>>> +    uint8_t *header;
>>> +    size_t   header_size;
>>> +    uint8_t *setup;
>>> +    size_t   setup_size;
>>> +} vorbis_new_extradata;
>>> +
>>>  /**
>>>   * Allocate and initialize the Vorbis parser using headers in the extradata.
>>>   */
>>> diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c
>>> index adbd726183..a4b159ba9b 100644
>>> --- a/libavcodec/vorbisdec.c
>>> +++ b/libavcodec/vorbisdec.c
>>> @@ -43,6 +43,7 @@
>>>  #include "vorbis.h"
>>>  #include "vorbisdsp.h"
>>>  #include "vorbis_data.h"
>>> +#include "vorbis_parser.h"
>>>  #include "xiph.h"
>>>
>>>  #define V_NB_BITS 8
>>> @@ -1778,47 +1779,59 @@ static int vorbis_decode_frame(AVCodecContext *avctx, AVFrame *frame,
>>>      GetBitContext *gb = &vc->gb;
>>>      float *channel_ptrs[255];
>>>      int i, len, ret;
>>> +    size_t new_extradata_size;
>>> +    vorbis_new_extradata *new_extradata;
>>> +    const uint8_t *header;
>>> +    const uint8_t *setup;
>>>
>>>      ff_dlog(NULL, "packet length %d \n", buf_size);
>>>
>>> -    if (*buf == 1 && buf_size > 7) {
>>> -        if ((ret = init_get_bits8(gb, buf + 1, buf_size - 1)) < 0)
>>> -            return ret;
>>> +    new_extradata = (vorbis_new_extradata *)av_packet_get_side_data(
>>> +        avpkt, AV_PKT_DATA_NEW_EXTRADATA, &new_extradata_size);
>>>
>>> -        vorbis_free(vc);
>>> -        if ((ret = vorbis_parse_id_hdr(vc))) {
>>> -            av_log(avctx, AV_LOG_ERROR, "Id header corrupt.\n");
>>> -            vorbis_free(vc);
>>> -            return ret;
>>> -        }
>>> +    if (new_extradata) {
>>> +        header = new_extradata->header;
>>> +        setup = new_extradata->setup;
>>>
>>> -        av_channel_layout_uninit(&avctx->ch_layout);
>>> -        if (vc->audio_channels > 8) {
>>> -            avctx->ch_layout.order       = AV_CHANNEL_ORDER_UNSPEC;
>>> -            avctx->ch_layout.nb_channels = vc->audio_channels;
>>> -        } else {
>>> -            av_channel_layout_copy(&avctx->ch_layout, &ff_vorbis_ch_layouts[vc->audio_channels - 1]);
>>> -        }
>>> +        if (new_extradata->header_size > 7 && *header == 1) {
>>> +            if ((ret = init_get_bits8(
>>> +                            gb, header + 1,
>>> +                            new_extradata->header_size - 1)) < 0)
>>> +                return ret;
>>>
>>> -        avctx->sample_rate = vc->audio_samplerate;
>>> -        return buf_size;
>>> -    }
>>> +            vorbis_free(vc);
>>> +            if ((ret = vorbis_parse_id_hdr(vc))) {
>>> +                av_log(avctx, AV_LOG_ERROR, "Id header corrupt.\n");
>>> +                vorbis_free(vc);
>>> +                return ret;
>>> +            }
>>>
>>> -    if (*buf == 3 && buf_size > 7) {
>>> -        av_log(avctx, AV_LOG_DEBUG, "Ignoring comment header\n");
>>> -        return buf_size;
>>> -    }
>>> +            av_channel_layout_uninit(&avctx->ch_layout);
>>> +            if (vc->audio_channels > 8) {
>>> +                avctx->ch_layout.order       = AV_CHANNEL_ORDER_UNSPEC;
>>> +                avctx->ch_layout.nb_channels = vc->audio_channels;
>>> +            } else {
>>> +                av_channel_layout_copy(
>>> +                    &avctx->ch_layout,
>>> +                    &ff_vorbis_ch_layouts[vc->audio_channels - 1]);
>>> +            }
>>>
>>> -    if (*buf == 5 && buf_size > 7 && vc->channel_residues && !vc->modes) {
>>> -        if ((ret = init_get_bits8(gb, buf + 1, buf_size - 1)) < 0)
>>> -            return ret;
>>> +            avctx->sample_rate = vc->audio_samplerate;
>>> +        }
>>>
>>> -        if ((ret = vorbis_parse_setup_hdr(vc))) {
>>> -            av_log(avctx, AV_LOG_ERROR, "Setup header corrupt.\n");
>>> -            vorbis_free(vc);
>>> -            return ret;
>>> +        if (new_extradata->setup_size > 7 && *setup == 5 &&
>>> +            vc->channel_residues && !vc->modes) {
>>> +            if ((ret = init_get_bits8(
>>> +                           gb, setup + 1,
>>> +                           new_extradata->setup_size - 1)) < 0)
>>> +                return ret;
>>> +
>>> +            if ((ret = vorbis_parse_setup_hdr(vc))) {
>>> +                av_log(avctx, AV_LOG_ERROR, "Setup header corrupt.\n");
>>> +                vorbis_free(vc);
>>> +                return ret;
>>> +            }
>>>          }
>>> -        return buf_size;
>>>      }
>>>
>>>      if (!vc->channel_residues || !vc->modes) {
>>> diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c
>>> index 62cc2da6de..f8e66e8127 100644
>>> --- a/libavformat/oggparsevorbis.c
>>> +++ b/libavformat/oggparsevorbis.c
>>> @@ -255,12 +255,19 @@ static void vorbis_cleanup(AVFormatContext *s, int idx)
>>>      struct ogg *ogg = s->priv_data;
>>>      struct ogg_stream *os = ogg->streams + idx;
>>>      struct oggvorbis_private *priv = os->private;
>>> +    vorbis_new_extradata *new_extradata;
>>>      int i;
>>>      if (os->private) {
>>>          av_vorbis_parse_free(&priv->vp);
>>>          for (i = 0; i < 3; i++)
>>>              av_freep(&priv->packet[i]);
>>>      }
>>> +
>>> +    if (os->new_extradata) {
>>> +        new_extradata = (vorbis_new_extradata *)os->new_extradata;
>>> +        av_freep(&new_extradata->header);
>>> +        av_freep(&new_extradata->setup);
>>> +    }
>>>  }
>>>
>>>  static int vorbis_update_metadata(AVFormatContext *s, int idx)
>>> @@ -433,7 +440,10 @@ static int vorbis_packet(AVFormatContext *s, int idx)
>>>      struct ogg *ogg = s->priv_data;
>>>      struct ogg_stream *os = ogg->streams + idx;
>>>      struct oggvorbis_private *priv = os->private;
>>> +    vorbis_new_extradata *new_extradata;
>>>      int duration, flags = 0;
>>> +    int skip_packet = 0;
>>> +    int ret;
>>>
>>>      if (!priv->vp)
>>>          return AVERROR_INVALIDDATA;
>>> @@ -496,10 +506,61 @@ static int vorbis_packet(AVFormatContext *s, int idx)
>>>          if (duration < 0) {
>>>              os->pflags |= AV_PKT_FLAG_CORRUPT;
>>>              return 0;
>>> -        } else if (flags & VORBIS_FLAG_COMMENT) {
>>> -            vorbis_update_metadata(s, idx);
>>> +        }
>>> +
>>> +        if (flags & VORBIS_FLAG_HEADER) {
>>> +            ret = vorbis_parse_header(s, s->streams[idx], os->buf + os->pstart, os->psize);
>>> +            if (ret < 0)
>>> +                return ret;
>>> +
>>> +            if (!os->new_extradata) {
>>> +                os->new_extradata = av_mallocz(sizeof(vorbis_new_extradata));
>>> +                if (!os->new_extradata)
>>> +                    return AVERROR(ENOMEM);
>>> +            }
>>> +
>>> +            os->new_extradata_size = sizeof(vorbis_new_extradata);
>>> +            new_extradata = (vorbis_new_extradata *)os->new_extradata;
>>> +
>>> +            ret = av_reallocp(&new_extradata->header, os->psize);
>>> +            if (ret < 0)
>>> +                return ret;
>>> +
>>> +            memcpy(new_extradata->header,  os->buf + os->pstart, os->psize);
>>> +            new_extradata->header_size = os->psize;
>>> +
>>> +            skip_packet = 1;
>>> +        }
>>> +
>>> +        if (flags & VORBIS_FLAG_COMMENT) {
>>> +            ret = vorbis_update_metadata(s, idx);
>>> +            if (ret < 0)
>>> +                return ret;
>>> +
>>>              flags = 0;
>>> +            skip_packet = 1;
>>> +        }
>>> +
>>> +        if (flags & VORBIS_FLAG_SETUP) {
>>> +            if (!os->new_extradata) {
>>> +                os->new_extradata = av_mallocz(sizeof(vorbis_new_extradata));
>>> +                if (!os->new_extradata)
>>> +                    return AVERROR(ENOMEM);
>>> +            }
>>> +
>>> +            os->new_extradata_size = sizeof(vorbis_new_extradata);
>>> +            new_extradata = (vorbis_new_extradata *)os->new_extradata;
>>> +
>>> +            ret = av_reallocp(&new_extradata->setup, os->psize);
>>> +            if (ret < 0)
>>> +                return ret;
>>> +
>>> +            memcpy(new_extradata->setup, os->buf + os->pstart, os->psize);
>>> +            new_extradata->setup_size = os->psize;
>>> +
>>> +            skip_packet = 1;
>>>          }
>>> +
>>>          os->pduration = duration;
>>>      }
>>>
>>> @@ -521,7 +582,7 @@ static int vorbis_packet(AVFormatContext *s, int idx)
>>>          priv->final_duration += os->pduration;
>>>      }
>>>
>>> -    return 0;
>>> +    return skip_packet;
>>>  }
>>>
>>>  const struct ogg_codec ff_vorbis_codec = {
>>
>> There are multiple issues with this patch:
> 
> Thank you for your feedback.
> 
>> 1. The side data structures are not padded, leading to
>> heap-buffer-overflows in the fate-ogg-vorbis-chained-meta test.
> 
> Do you have a pointer to this issue? Is there a failing test here:
> https://fate.ffmpeg.org/ ?
> 

I noted it when I ran FATE with (Clang-)ASAN locally. Seems like none of
the ASAN/valgrind fate boxes tested your commit.

>> 2. The side data structures are not flat and therefore not suitable for
>> use as AVPacketSideData. (The setup and header arrays are currently
>> owned by the demuxer, yet an AVPacket is supposed to be valid on its
>> own. But this side data becomes invalid when the demuxer encounters a
>> new side data (and reallocates its internal buffers) or when the demuxer
>> is closed.)
> 
> I can work on that.

Actually, thinking about this a bit more: New extradata via side data
should use the same format as ordinary extradata, so there is no need to
add a new struct and APIchanges for that.

- Andreas

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