Re: [FFmpeg-devel] [PATCH] avformat/mov: add ignore_hoov option to ignore hoov atom

[Steven Liu <lq@chinaffmpeg.org>]

> 2021年12月24日 上午11:43，zhilizhao(赵志立) <quinkblack@foxmail.com> 写道：
> 
> 
> 
>> On Dec 23, 2021, at 3:10 PM, Steven Liu <lq@chinaffmpeg.org> wrote:
>> 
>> Try to get context from the moov atom when the hoov before moov atom,
>> because the streams info get a possible incorrect when there have both
>> hoov and moov atom. So add and ignore_hoov option for try to get
>> moov context by user.
>> 
>> Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
>> ---
>> doc/demuxers.texi  |  6 ++++++
>> libavformat/isom.h |  2 ++
>> libavformat/mov.c  | 14 ++++++++++++--
>> 3 files changed, 20 insertions(+), 2 deletions(-)
>> 
>> diff --git a/doc/demuxers.texi b/doc/demuxers.texi
>> index cab8a7072c..d23c118210 100644
>> --- a/doc/demuxers.texi
>> +++ b/doc/demuxers.texi
>> @@ -660,6 +660,11 @@ to demuxing linearly from the beginning. Default is true.
>> Ignore any edit list atoms. The demuxer, by default, modifies the stream index to reflect the
>> timeline described by the edit list. Default is false.
>> 
>> +@item ignore_hoov
>> +Ignore hoov atom. The demuxer, by default, use hoov atom when there have hoov before moov atom.
>> +You can try ignore hoov atom try the moov atom.
>> +Default is false.
>> +
>> @item advanced_editlist
>> Modify the stream index to reflect the timeline described by the edit list. @code{ignore_editlist}
>> must be set to false for this option to be effective.
>> diff --git a/libavformat/isom.h b/libavformat/isom.h
>> index ef8f19b18c..6aa2b40c94 100644
>> --- a/libavformat/isom.h
>> +++ b/libavformat/isom.h
>> @@ -255,6 +255,7 @@ typedef struct MOVContext {
>>    AVFormatContext *fc;
>>    int time_scale;
>>    int64_t duration;     ///< duration of the longest track
>> +    int found_hoov;       ///< 'hoov' atom has been found
>>    int found_moov;       ///< 'moov' atom has been found
>>    int found_mdat;       ///< 'mdat' atom has been found
>>    int found_hdlr_mdta;  ///< 'hdlr' atom with type 'mdta' has been found
>> @@ -273,6 +274,7 @@ typedef struct MOVContext {
>>    unsigned int nb_chapter_tracks;
>>    int use_absolute_path;
>>    int ignore_editlist;
>> +    int ignore_hoov;
>>    int advanced_editlist;
>>    int ignore_chapters;
>>    int seek_individually;
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index 2aed6e80ef..cd775b219f 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -1159,8 +1159,11 @@ static int mov_read_moov(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>> 
>>    if (c->found_moov) {
>>        av_log(c->fc, AV_LOG_WARNING, "Found duplicated MOOV Atom. Skipped it\n");
>> -        avio_skip(pb, atom.size);
>> -        return 0;
>> +        if (!c->found_hoov) {
>> +            avio_skip(pb, atom.size);
>> +            return 0;
>> +        }
>> +        c->found_hoov = 0;
>>    }
>> 
>>    if ((ret = mov_read_default(c, pb, atom)) < 0)
>> @@ -4239,6 +4242,9 @@ static int mov_read_trak(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>    MOVStreamContext *sc;
>>    int ret;
>> 
>> +    if (c->found_hoov)
>> +        return 0;
>> +
> 
> Does it break files with only hoov boxes?
No by default. And Yes if have both hoov and moov.
Yes it should break if user use ignore_hoov option.
Add ignore_hoov can be choosed by users.

>  
>>    st = avformat_new_stream(c->fc, NULL);
>>    if (!st) return AVERROR(ENOMEM);
>>    st->id = -1;
>> @@ -7329,6 +7335,8 @@ static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>                a.size >= 8 &&
>>                c->fc->strict_std_compliance < FF_COMPLIANCE_STRICT) {
>>                uint32_t type;
>> +                if (c->ignore_hoov)
>> +                    c->found_hoov = 1;
>>                avio_skip(pb, 4);
>>                type = avio_rl32(pb);
>>                if (avio_feof(pb))
>> @@ -8541,6 +8549,8 @@ static const AVOption mov_options[] = {
>>        0, 1, FLAGS},
>>    {"ignore_editlist", "Ignore the edit list atom.", OFFSET(ignore_editlist), AV_OPT_TYPE_BOOL, {.i64 = 0},
>>        0, 1, FLAGS},
>> +    {"ignore_hoov", "Ignore the hoov atom.", OFFSET(ignore_hoov), AV_OPT_TYPE_BOOL, {.i64 = 0},
>> +        0, 1, FLAGS},
> 
> TBH, add an option is too much effort to workaround such broken files. I prefer
> 
> a.type == MKTAG('h','o','o','v') && c->fc->strict_std_compliance < FF_COMPLIANCE_UNOFFICIAL
> 
> But it will break those samples if user doesn't lower strict_std_compliance.
> 
>>    {"advanced_editlist",
>>        "Modify the AVIndex according to the editlists. Use this option to decode in the order specified by the edits.",
>>        OFFSET(advanced_editlist), AV_OPT_TYPE_BOOL, {.i64 = 1},
>> -- 
>> 2.25.0
>> 
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Thanks

Steven Liu

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