[FFmpeg-devel] [PATCH] avformat/hls: Fixes overwriting existing #EXT-X-PROGRAM-DATE-TIME value in HLS playlist
Steven Liu
lq at chinaffmpeg.org
Thu Nov 26 04:29:47 EET 2020
> 2020年11月25日 下午9:57，Vignesh Ravichandran <vignesh.ravichandran02 at gmail.com> 写道：
>
> Sure, how about the snippet below:
>
> regex_t regex;
> regcomp(®ex,
> "([12][0-9]{3}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])T([01][1-9]|2[0-3]):([0-5][0-9]):([0-5][0-9]).([0-9]{3}))",
> REG_EXTENDED);
> if (regexec(®ex, ptr, 0, NULL, 0) == REG_NOMATCH) {
> ret = AVERROR_INVALIDDATA;
> goto fail;
> }
Define a new function to check the value:
1. Split the string by ‘-‘
2. Check every value splited by ‘-‘
3. If the value is int, that is correct result.
4. Else not.
>
> On Wed, Nov 25, 2020 at 5:31 PM Steven Liu <lq at chinaffmpeg.org> wrote:
>
>>
>>
>>> 2020年11月25日 下午7:49，Vignesh Ravichandran <
>> vignesh.ravichandran02 at gmail.com> 写道：
>>>
>>> We could add a simple check like below to prevent it:
>>>
>>> if (sscanf(ptr, "%d-%d-%dT%d:%d:%d.%lf", &y, &M, &d, &h, &m, &s, &ms) !=
>> 7)
>>> {
>>> ret = AVERROR_INVALIDDATA;
>>> goto fail;
>>> }
>>>
>>> Please let me know.
>> Not sure this is better way, what about validate the string of the
>> "#EXT-X-PROGRAM-DATE-TIME” values？
>>>
>>>
>>> Thanks,
>>> Vignesh
>>>
>>> On Wed, Nov 25, 2020 at 11:29 AM Steven Liu <lq at chinaffmpeg.org> wrote:
>>>
>>>>
>>>>
>>>>> 2020年11月25日 下午1:16，Vignesh Ravichandran <
>>>> vignesh.ravichandran02 at gmail.com> 写道：
>>>>>
>>>>> Bug ID: 8989
>>>>>
>>>>> This is is due to the following behavior in the current code:
>>>>> 1. The initial_prog_date_time gets set to the current local time
>>>>> 2. The existing playlist (.m3u8) file gets parsed and the segments
>>>> present are added to the variant stream
>>>>> 3. The new segment is created and added
>>>>> 4. The existing segments and the new segment are written to the
>> playlist
>>>> file. The initial_prog_date_time from point 1 is used for calculating
>>>> "#EXT-X-PROGRAM-DATE-TIME" for the segments, which results in incorrect
>>>> "#EXT-X-PROGRAM-DATE-TIME" values for existing segments
>>>>>
>>>>> The following approach fixes this bug:
>>>>> 1. Add a new variable "discont_program_date_time" of type double to
>>>> HLSSegment struct
>>>>> 2. Store the "EXT-X-PROGRAM-DATE-TIME" value from the existing segments
>>>> in this variable
>>>>> 3. When writing to playlist file if "discont_program_date_time" is set,
>>>> then use that value for "EXT-X-PROGRAM-DATE-TIME" else use the value
>>>> present in vs->initial_prog_date_time
>>>>>
>>>>> Signed-off-by: Vignesh Ravichandran <vignesh.ravichandran02 at gmail.com>
>>>>> ---
>>>>> libavformat/hlsenc.c | 35 +++++++++++++++++++++++++++++++----
>>>>> 1 file changed, 31 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
>>>>> index cbfd8f7c0d..030a2d3b97 100644
>>>>> --- a/libavformat/hlsenc.c
>>>>> +++ b/libavformat/hlsenc.c
>>>>> @@ -88,6 +88,7 @@ typedef struct HLSSegment {
>>>>> char iv_string[KEYSIZE*2 + 1];
>>>>>
>>>>> struct HLSSegment *next;
>>>>> + double discont_program_date_time;
>>>>> } HLSSegment;
>>>>>
>>>>> typedef enum HLSFlags {
>>>>> @@ -1124,6 +1125,7 @@ static int hls_append_segment(struct
>>>> AVFormatContext *s, HLSContext *hls,
>>>>> en->keyframe_size = vs->video_keyframe_size;
>>>>> en->next = NULL;
>>>>> en->discont = 0;
>>>>> + en->discont_program_date_time = 0;
>>>>>
>>>>> if (vs->discontinuity) {
>>>>> en->discont = 1;
>>>>> @@ -1148,7 +1150,8 @@ static int hls_append_segment(struct
>>>> AVFormatContext *s, HLSContext *hls,
>>>>>
>>>>> if (hls->max_nb_segments && vs->nb_entries >= hls->max_nb_segments)
>> {
>>>>> en = vs->segments;
>>>>> - vs->initial_prog_date_time += en->duration;
>>>>> + if (!en->next->discont_program_date_time &&
>>>> !en->discont_program_date_time)
>>>>> + vs->initial_prog_date_time += en->duration;
>>>>> vs->segments = en->next;
>>>>> if (en && hls->flags & HLS_DELETE_SEGMENTS &&
>>>>> #if FF_API_HLS_WRAP
>>>>> @@ -1182,6 +1185,8 @@ static int parse_playlist(AVFormatContext *s,
>>>> const char *url, VariantStream *vs
>>>>> char line[MAX_URL_SIZE];
>>>>> const char *ptr;
>>>>> const char *end;
>>>>> + int is_discont_detected = 0;
>>>>> + double discont_program_date_time = 0;
>>>>>
>>>>> if ((ret = ffio_open_whitelist(&in, url, AVIO_FLAG_READ,
>>>>> &s->interrupt_callback, NULL,
>>>>> @@ -1211,6 +1216,7 @@ static int parse_playlist(AVFormatContext *s,
>>>> const char *url, VariantStream *vs
>>>>> } else if (av_strstart(line, "#EXT-X-DISCONTINUITY", &ptr)) {
>>>>> is_segment = 1;
>>>>> vs->discontinuity = 1;
>>>>> + is_discont_detected = 1;
>>>>> } else if (av_strstart(line, "#EXTINF:", &ptr)) {
>>>>> is_segment = 1;
>>>>> vs->duration = atof(ptr);
>>>>> @@ -1236,7 +1242,23 @@ static int parse_playlist(AVFormatContext *s,
>>>> const char *url, VariantStream *vs
>>>>> av_strlcpy(vs->iv_string, ptr,
>>>> sizeof(vs->iv_string));
>>>>> }
>>>>> }
>>>>> -
>>>>> + } else if (av_strstart(line, "#EXT-X-PROGRAM-DATE-TIME:",
>> &ptr)
>>>> && is_discont_detected) {
>>>>> + struct tm program_date_time;
>>>>> + int y,M,d,h,m,s;
>>>>> + double ms;
>>>>> + sscanf(ptr, "%d-%d-%dT%d:%d:%d.%lf", &y, &M, &d, &h, &m,
>>>> &s, &ms);
>>>> What will happen if I modify the value of “EXT-X-PROGRAM-DATE-TIME” by
>>>> hacker,
>>>> For example:
>>>> #EXT-X-PROGRAM-DATA-TIME: good-morning-ladies-and-gentlemen.
>>>>
>>>>> +
>>>>> + program_date_time.tm_year = y - 1900;
>>>>> + program_date_time.tm_mon = M - 1;
>>>>> + program_date_time.tm_mday = d;
>>>>> + program_date_time.tm_hour = h;
>>>>> + program_date_time.tm_min = m;
>>>>> + program_date_time.tm_sec = s;
>>>>> + program_date_time.tm_isdst = -1;
>>>>> +
>>>>> + discont_program_date_time = mktime(&program_date_time);
>>>>> + discont_program_date_time += (double)(ms / 1000);
>>>>> + is_discont_detected = 0;
>>>>> } else if (av_strstart(line, "#", NULL)) {
>>>>> continue;
>>>>> } else if (line[0]) {
>>>>> @@ -1250,8 +1272,9 @@ static int parse_playlist(AVFormatContext *s,
>>>> const char *url, VariantStream *vs
>>>>> is_segment = 0;
>>>>> new_start_pos = avio_tell(vs->avf->pb);
>>>>> vs->size = new_start_pos - vs->start_pos;
>>>>> - vs->initial_prog_date_time -= vs->duration; // this is
>>>> a previously existing segment
>>>>> ret = hls_append_segment(s, hls, vs, vs->duration,
>>>> vs->start_pos, vs->size);
>>>>> + vs->last_segment->discont_program_date_time =
>>>> discont_program_date_time;
>>>>> + discont_program_date_time += vs->duration;
>>>>> if (ret < 0)
>>>>> goto fail;
>>>>> vs->start_pos = new_start_pos;
>>>>> @@ -1572,7 +1595,11 @@ static int hls_window(AVFormatContext *s, int
>>>> last, VariantStream *vs)
>>>>> ret = ff_hls_write_file_entry(byterange_mode ? hls->m3u8_out :
>>>> vs->out, en->discont, byterange_mode,
>>>>> en->duration, hls->flags &
>>>> HLS_ROUND_DURATIONS,
>>>>> en->size, en->pos, hls->baseurl,
>>>>> - en->filename, prog_date_time_p,
>>>> en->keyframe_size, en->keyframe_pos, hls->flags & HLS_I_FRAMES_ONLY);
>>>>> + en->filename,
>>>>> + en->discont_program_date_time ?
>>>> &en->discont_program_date_time : prog_date_time_p,
>>>>> + en->keyframe_size,
>>>> en->keyframe_pos, hls->flags & HLS_I_FRAMES_ONLY);
>>>>> + if (en->discont_program_date_time)
>>>>> + en->discont_program_date_time -= en->duration;
>>>>> if (ret < 0) {
>>>>> av_log(s, AV_LOG_WARNING, "ff_hls_write_file_entry get
>>>> error\n");
>>>>> }
>>>>> --
>>>>> 2.24.2 (Apple Git-127)
>>>>>
>>>>> _______________________________________________
>>>>> ffmpeg-devel mailing list
>>>>> ffmpeg-devel at ffmpeg.org
>>>>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>>>>
>>>>> To unsubscribe, visit link above, or email
>>>>> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>>>>
>>>> Thanks
>>>>
>>>> Steven Liu
>>>>
>>>>
>>>>
>>>>
>>> _______________________________________________
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>>
>> Thanks
>>
>> Steven Liu
>>
>>
>>
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Thanks
Steven Liu
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